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Before you begin, make sure you have all the necessary libraries installed: pip install transformers datasets evaluate We encourage you to log in to your Hugging Face account so you can upload and share your model with the community. When prompted, enter your token to log in: from huggingface_hub import notebook_login notebook_login() Load ELI5 dataset Start by loading a smaller subset of the r/askscience subset of the ELI5 dataset from the 🤗 Datasets library. This'll give you a chance to experiment and make sure everything works before spending more time training on the full dataset. from datasets import load_dataset eli5 = load_dataset("eli5", split="train_asks[:5000]") Split the dataset's train_asks split into a train and test set with the [~datasets.Dataset.train_test_split] method: eli5 = eli5.train_test_split(test_size=0.2) Then take a look at an example: eli5["train"][0] {'answers': {'a_id': ['c3d1aib', 'c3d4lya'], 'score': [6, 3], 'text': ["The velocity needed to remain in orbit is equal to the square root of Newton's constant times the mass of earth divided by the distance from the center of the earth. I don't know the altitude of that specific mission, but they're usually around 300 km. That means he's going 7-8 km/s.\n\nIn space there are no other forces acting on either the shuttle or the guy, so they stay in the same position relative to each other. If he were to become unable to return to the ship, he would presumably run out of oxygen, or slowly fall into the atmosphere and burn up.", "Hope you don't mind me asking another question, but why aren't there any stars visible in this photo?"]}, 'answers_urls': {'url': []}, 'document': '', 'q_id': 'nyxfp', 'selftext': 'URL_0\n\nThis was on the front page earlier and I have a few questions about it. Is it possible to calculate how fast the astronaut would be orbiting the earth? Also how does he stay close to the shuttle so that he can return safely, i.e is he orbiting at the same speed and can therefore stay next to it? And finally if his propulsion system failed, would he eventually re-enter the atmosphere and presumably die?', 'selftext_urls': {'url': ['http://apod.nasa.gov/apod/image/1201/freeflyer_nasa_3000.jpg']}, 'subreddit': 'askscience', 'title': 'Few questions about this space walk photograph.', 'title_urls': {'url': []}} While this may look like a lot, you're only really interested in the text field. What's cool about language modeling tasks is you don't need labels (also known as an unsupervised task) because the next word is the label. Preprocess For masked language modeling, the next step is to load a DistilRoBERTa tokenizer to process the text subfield: from transformers import AutoTokenizer tokenizer = AutoTokenizer.from_pretrained("distilroberta-base") You'll notice from the example above, the text field is actually nested inside answers. This means you'll need to e xtract the text subfield from its nested structure with the flatten method: eli5 = eli5.flatten() eli5["train"][0] {'answers.a_id': ['c3d1aib', 'c3d4lya'], 'answers.score': [6, 3], 'answers.text': ["The velocity needed to remain in orbit is equal to the square root of Newton's constant times the mass of earth divided by the distance from the center of the earth. I don't know the altitude of that specific mission, but they're usually around 300 km. That means he's going 7-8 km/s.\n\nIn space there are no other forces acting on either the shuttle or the guy, so they stay in the same position relative to each other. If he were to become unable to return to the ship, he would presumably run out of oxygen, or slowly fall into the atmosphere and burn up.", "Hope you don't mind me asking another question, but why aren't there any stars visible in this photo?"], 'answers_urls.url': [], 'document': '', 'q_id': 'nyxfp', 'selftext': 'URL_0\n\nThis was on the front page earlier and I have a few questions about it. Is it possible to calculate how fast the astronaut would be orbiting the earth? Also how does he stay close to the shuttle so that he can return safely, i.e is he orbiting at the same speed and can therefore stay next to it? And finally if his propulsion system failed, would he eventually re-enter the atmosphere and presumably die?', 'selftext_urls.url': ['http://apod.nasa.gov/apod/image/1201/freeflyer_nasa_3000.jpg'], 'subreddit': 'askscience', 'title': 'Few questions about this space walk photograph.', 'title_urls.url': []} Each subfield is now a separate column as indicated by the answers prefix, and the text field is a list now. Instead of tokenizing each sentence separately, convert the list to a string so you can jointly tokenize them. Here is a first preprocessing function to join the list of strings for each example and tokenize the result: def preprocess_function(examples): return tokenizer([" ".join(x) for x in examples["answers.text"]]) To apply this preprocessing function over the entire dataset, use the 🤗 Datasets [~datasets.Dataset.map] method. You can speed up the map function by setting batched=True to process multiple elements of the dataset at once, and increasing the number of processes with num_proc. Remove any columns you don't need: tokenized_eli5 = eli5.map( preprocess_function, batched=True, num_proc=4, remove_columns=eli5["train"].column_names, ) This dataset contains the token sequences, but some of these are longer than the maximum input length for the model. You can now use a second preprocessing function to - concatenate all the sequences - split the concatenated sequences into shorter chunks defined by block_size, which should be both shorter than the maximum input length and short enough for your GPU RAM. block_size = 128 def group_texts(examples): # Concatenate all texts. concatenated_examples = {k: sum(examples[k], []) for k in examples.keys()} total_length = len(concatenated_examples[list(examples.keys())[0]]) # We drop the small remainder, we could add padding if the model supported it instead of this drop, you can # customize this part to your needs. if total_length >= block_size: total_length = (total_length // block_size) * block_size # Split by chunks of block_size. result = { k: [t[i : i + block_size] for i in range(0, total_length, block_size)] for k, t in concatenated_examples.items() } return result Apply the group_texts function over the entire dataset: lm_dataset = tokenized_eli5.map(group_texts, batched=True, num_proc=4) Now create a batch of examples using [DataCollatorForLanguageModeling]. It's more efficient to dynamically pad the sentences to the longest length in a batch during collation, instead of padding the whole dataset to the maximum length. Use the end-of-sequence token as the padding token and specify mlm_probability to randomly mask tokens each time you iterate over the data: from transformers import DataCollatorForLanguageModeling tokenizer.pad_token = tokenizer.eos_token data_collator = DataCollatorForLanguageModeling(tokenizer=tokenizer, mlm_probability=0.15) Use the end-of-sequence token as the padding token and specify mlm_probability to randomly mask tokens each time you iterate over the data: from transformers import DataCollatorForLanguageModeling data_collator = DataCollatorForLanguageModeling(tokenizer=tokenizer, mlm_probability=0.15, return_tensors="tf") Train If you aren't familiar with finetuning a model with the [Trainer], take a look at the basic tutorial here! You're ready to start training your model now! Load DistilRoBERTa with [AutoModelForMaskedLM]: from transformers import AutoModelForMaskedLM model = AutoModelForMaskedLM.from_pretrained("distilroberta-base") At this point, only three steps remain: Define your training hyperparameters in [TrainingArguments]. The only required parameter is output_dir which specifies where to save your model. You'll push this model to the Hub by setting push_to_hub=True (you need to be signed in to Hugging Face to upload your model). Pass the training arguments to [Trainer] along with the model, datasets, and data collator. Call [~Trainer.train] to finetune your model. training_args = TrainingArguments( output_dir="my_awesome_eli5_mlm_model", evaluation_strategy="epoch", learning_rate=2e-5, num_train_epochs=3, weight_decay=0.01, push_to_hub=True, ) trainer = Trainer( model=model, args=training_args, train_dataset=lm_dataset["train"], eval_dataset=lm_dataset["test"], data_collator=data_collator, ) trainer.train() Once training is completed, use the [~transformers.Trainer.evaluate] method to evaluate your model and get its perplexity: import math eval_results = trainer.evaluate() print(f"Perplexity: {math.exp(eval_results['eval_loss']):.2f}") Perplexity: 8.76 Then share your model to the Hub with the [~transformers.Trainer.push_to_hub] method so everyone can use your model: trainer.push_to_hub() If you aren't familiar with finetuning a model with Keras, take a look at the basic tutorial here! To finetune a model in TensorFlow, start by setting up an optimizer function, learning rate schedule, and some training hyperparameters: from transformers import create_optimizer, AdamWeightDecay optimizer = AdamWeightDecay(learning_rate=2e-5, weight_decay_rate=0.01) Then you can load DistilRoBERTa with [TFAutoModelForMaskedLM]: from transformers import TFAutoModelForMaskedLM model = TFAutoModelForMaskedLM.from_pretrained("distilroberta-base") Convert your datasets to the tf.data.Dataset format with [~transformers.TFPreTrainedModel.prepare_tf_dataset]: tf_train_set = model.prepare_tf_dataset( lm_dataset["train"], shuffle=True, batch_size=16, collate_fn=data_collator, ) tf_test_set = model.prepare_tf_dataset( lm_dataset["test"], shuffle=False, batch_size=16, collate_fn=data_collator, ) Configure the model for training with compile. Note that Transformers models all have a default task-relevant loss function, so you don't need to specify one unless you want to: import tensorflow as tf model.compile(optimizer=optimizer) # No loss argument! This can be done by specifying where to push your model and tokenizer in the [~transformers.PushToHubCallback]: from transformers.keras_callbacks import PushToHubCallback callback = PushToHubCallback( output_dir="my_awesome_eli5_mlm_model", tokenizer=tokenizer, ) Finally, you're ready to start training your model! Call fit with your training and validation datasets, the number of epochs, and your callback to finetune the model: model.fit(x=tf_train_set, validation_data=tf_test_set, epochs=3, callbacks=[callback]) Once training is completed, your model is automatically uploaded to the Hub so everyone can use it! For a more in-depth example of how to finetune a model for masked language modeling, take a look at the corresponding PyTorch notebook or TensorFlow notebook. Inference Great, now that you've finetuned a model, you can use it for inference! Come up with some text you'd like the model to fill in the blank with, and use the special <mask> token to indicate the blank: text = "The Milky Way is a galaxy." The simplest way to try out your finetuned model for inference is to use it in a [pipeline]. Instantiate a pipeline for fill-mask with your model, and pass your text to it. If you like, you can use the top_k parameter to specify how many predictions to return: from transformers import pipeline mask_filler = pipeline("fill-mask", "stevhliu/my_awesome_eli5_mlm_model") mask_filler(text, top_k=3) [{'score': 0.5150994658470154, 'token': 21300, 'token_str': ' spiral', 'sequence': 'The Milky Way is a spiral galaxy.'}, {'score': 0.07087188959121704, 'token': 2232, 'token_str': ' massive', 'sequence': 'The Milky Way is a massive galaxy.'}, {'score': 0.06434620916843414, 'token': 650, 'token_str': ' small', 'sequence': 'The Milky Way is a small galaxy.'}] Tokenize the text and return the input_ids as PyTorch tensors. You'll also need to specify the position of the <mask> token: from transformers import AutoTokenizer tokenizer = AutoTokenizer.from_pretrained("stevhliu/my_awesome_eli5_mlm_model") inputs = tokenizer(text, return_tensors="pt") mask_token_index = torch.where(inputs["input_ids"] == tokenizer.mask_token_id)[1] Pass your inputs to the model and return the logits of the masked token: from transformers import AutoModelForMaskedLM model = AutoModelForMaskedLM.from_pretrained("stevhliu/my_awesome_eli5_mlm_model") logits = model(**inputs).logits mask_token_logits = logits[0, mask_token_index, :] Then return the three masked tokens with the highest probability and print them out: top_3_tokens = torch.topk(mask_token_logits, 3, dim=1).indices[0].tolist() for token in top_3_tokens: print(text.replace(tokenizer.mask_token, tokenizer.decode([token]))) The Milky Way is a spiral galaxy. The Milky Way is a massive galaxy. The Milky Way is a small galaxy. `` </pt> <tf> Tokenize the text and return theinput_idsas TensorFlow tensors. You'll also need to specify the position of the` token: from transformers import AutoTokenizer tokenizer = AutoTokenizer.from_pretrained("stevhliu/my_awesome_eli5_mlm_model") inputs = tokenizer(text, return_tensors="tf") mask_token_index = tf.where(inputs["input_ids"] == tokenizer.mask_token_id)[0, 1] Pass your inputs to the model and return the logits of the masked token: from transformers import TFAutoModelForMaskedLM model = TFAutoModelForMaskedLM.from_pretrained("stevhliu/my_awesome_eli5_mlm_model") logits = model(**inputs).logits mask_token_logits = logits[0, mask_token_index, :] Then return the three masked tokens with the highest probability and print them out: top_3_tokens = tf.math.top_k(mask_token_logits, 3).indices.numpy() for token in top_3_tokens: print(text.replace(tokenizer.mask_token, tokenizer.decode([token]))) The Milky Way is a spiral galaxy. The Milky Way is a massive galaxy. The Milky Way is a small galaxy.

Efficient Inference on CPU This guide focuses on inferencing large models efficiently on CPU. BetterTransformer for faster inference We have recently integrated BetterTransformer for faster inference on CPU for text, image and audio models. Check the documentation about this integration here for more details. PyTorch JIT-mode (TorchScript) TorchScript is a way to create serializable and optimizable models from PyTorch code. Any TorchScript program can be saved from a Python process and loaded in a process where there is no Python dependency. Comparing to default eager mode, jit mode in PyTorch normally yields better performance for model inference from optimization methodologies like operator fusion. For a gentle introduction to TorchScript, see the Introduction to PyTorch TorchScript tutorial. IPEX Graph Optimization with JIT-mode Intel® Extension for PyTorch provides further optimizations in jit mode for Transformers series models. It is highly recommended for users to take advantage of Intel® Extension for PyTorch with jit mode. Some frequently used operator patterns from Transformers models are already supported in Intel® Extension for PyTorch with jit mode fusions. Those fusion patterns like Multi-head-attention fusion, Concat Linear, Linear+Add, Linear+Gelu, Add+LayerNorm fusion and etc. are enabled and perform well. The benefit of the fusion is delivered to users in a transparent fashion. According to the analysis, ~70% of most popular NLP tasks in question-answering, text-classification, and token-classification can get performance benefits with these fusion patterns for both Float32 precision and BFloat16 Mixed precision. Check more detailed information for IPEX Graph Optimization. IPEX installation: IPEX release is following PyTorch, check the approaches for IPEX installation. Usage of JIT-mode To enable JIT-mode in Trainer for evaluaion or prediction, users should add jit_mode_eval in Trainer command arguments. for PyTorch >= 1.14.0. JIT-mode could benefit any models for prediction and evaluaion since dict input is supported in jit.trace for PyTorch < 1.14.0. JIT-mode could benefit models whose forward parameter order matches the tuple input order in jit.trace, like question-answering model In the case where the forward parameter order does not match the tuple input order in jit.trace, like text-classification models, jit.trace will fail and we are capturing this with the exception here to make it fallback. Logging is used to notify users. Take an example of the use cases on Transformers question-answering Inference using jit mode on CPU: python run_qa.py \ --model_name_or_path csarron/bert-base-uncased-squad-v1 \ --dataset_name squad \ --do_eval \ --max_seq_length 384 \ --doc_stride 128 \ --output_dir /tmp/ \ --no_cuda \ --jit_mode_eval Inference with IPEX using jit mode on CPU: python run_qa.py \ --model_name_or_path csarron/bert-base-uncased-squad-v1 \ --dataset_name squad \ --do_eval \ --max_seq_length 384 \ --doc_stride 128 \ --output_dir /tmp/ \ --no_cuda \ --use_ipex \ --jit_mode_eval

Attention mechanisms Most transformer models use full attention in the sense that the attention matrix is square. It can be a big computational bottleneck when you have long texts. Longformer and reformer are models that try to be more efficient and use a sparse version of the attention matrix to speed up training. LSH attention Reformer uses LSH attention. In the softmax(QK^t), only the biggest elements (in the softmax dimension) of the matrix QK^t are going to give useful contributions. So for each query q in Q, we can consider only the keys k in K that are close to q. A hash function is used to determine if q and k are close. The attention mask is modified to mask the current token (except at the first position), because it will give a query and a key equal (so very similar to each other). Since the hash can be a bit random, several hash functions are used in practice (determined by a n_rounds parameter) and then are averaged together. Local attention Longformer uses local attention: often, the local context (e.g., what are the two tokens to the left and right?) is enough to take action for a given token. Also, by stacking attention layers that have a small window, the last layer will have a receptive field of more than just the tokens in the window, allowing them to build a representation of the whole sentence. Some preselected input tokens are also given global attention: for those few tokens, the attention matrix can access all tokens and this process is symmetric: all other tokens have access to those specific tokens (on top of the ones in their local window). This is shown in Figure 2d of the paper, see below for a sample attention mask: Using those attention matrices with less parameters then allows the model to have inputs having a bigger sequence length. Other tricks Axial positional encodings Reformer uses axial positional encodings: in traditional transformer models, the positional encoding E is a matrix of size \(l\) by \(d\), \(l\) being the sequence length and \(d\) the dimension of the hidden state. If you have very long texts, this matrix can be huge and take way too much space on the GPU. To alleviate that, axial positional encodings consist of factorizing that big matrix E in two smaller matrices E1 and E2, with dimensions \(l_{1} \times d_{1}\) and \(l_{2} \times d_{2}\), such that \(l_{1} \times l_{2} = l\) and \(d_{1} + d_{2} = d\) (with the product for the lengths, this ends up being way smaller). The embedding for time step \(j\) in E is obtained by concatenating the embeddings for timestep \(j \% l1\) in E1 and \(j // l1\) in E2.

How to convert a 🤗 Transformers model to TensorFlow? Having multiple frameworks available to use with 🤗 Transformers gives you flexibility to play their strengths when designing your application, but it implies that compatibility must be added on a per-model basis. The good news is that adding TensorFlow compatibility to an existing model is simpler than adding a new model from scratch! Whether you wish to have a deeper understanding of large TensorFlow models, make a major open-source contribution, or enable TensorFlow for your model of choice, this guide is for you. This guide empowers you, a member of our community, to contribute TensorFlow model weights and/or architectures to be used in 🤗 Transformers, with minimal supervision from the Hugging Face team. Writing a new model is no small feat, but hopefully this guide will make it less of a rollercoaster 🎢 and more of a walk in the park 🚶. Harnessing our collective experiences is absolutely critical to make this process increasingly easier, and thus we highly encourage that you suggest improvements to this guide! Before you dive deeper, it is recommended that you check the following resources if you're new to 🤗 Transformers: - General overview of 🤗 Transformers - Hugging Face's TensorFlow Philosophy In the remainder of this guide, you will learn what's needed to add a new TensorFlow model architecture, the procedure to convert PyTorch into TensorFlow model weights, and how to efficiently debug mismatches across ML frameworks. Let's get started! Are you unsure whether the model you wish to use already has a corresponding TensorFlow architecture?   Check the model_type field of the config.json of your model of choice (example). If the corresponding model folder in 🤗 Transformers has a file whose name starts with "modeling_tf", it means that it has a corresponding TensorFlow architecture (example). Step-by-step guide to add TensorFlow model architecture code There are many ways to design a large model architecture, and multiple ways of implementing said design. However, you might recall from our general overview of 🤗 Transformers that we are an opinionated bunch - the ease of use of 🤗 Transformers relies on consistent design choices. From experience, we can tell you a few important things about adding TensorFlow models: Don't reinvent the wheel! More often that not, there are at least two reference implementations you should check: the PyTorch equivalent of the model you are implementing and other TensorFlow models for the same class of problems. Great model implementations survive the test of time. This doesn't happen because the code is pretty, but rather because the code is clear, easy to debug and build upon. If you make the life of the maintainers easy with your TensorFlow implementation, by replicating the same patterns as in other TensorFlow models and minimizing the mismatch to the PyTorch implementation, you ensure your contribution will be long lived. Ask for help when you're stuck! The 🤗 Transformers team is here to help, and we've probably found solutions to the same problems you're facing. Here's an overview of the steps needed to add a TensorFlow model architecture: 1. Select the model you wish to convert 2. Prepare transformers dev environment 3. (Optional) Understand theoretical aspects and the existing implementation 4. Implement the model architecture 5. Implement model tests 6. Submit the pull request 7. (Optional) Build demos and share with the world 1.-3. Prepare your model contribution 1. Select the model you wish to convert Let's start off with the basics: the first thing you need to know is the architecture you want to convert. If you don't have your eyes set on a specific architecture, asking the 🤗 Transformers team for suggestions is a great way to maximize your impact - we will guide you towards the most prominent architectures that are missing on the TensorFlow side. If the specific model you want to use with TensorFlow already has a TensorFlow architecture implementation in 🤗 Transformers but is lacking weights, feel free to jump straight into the weight conversion section of this page. For simplicity, the remainder of this guide assumes you've decided to contribute with the TensorFlow version of BrandNewBert (the same example as in the guide to add a new model from scratch). Before starting the work on a TensorFlow model architecture, double-check that there is no ongoing effort to do so. You can search for BrandNewBert on the pull request GitHub page to confirm that there is no TensorFlow-related pull request. 2. Prepare transformers dev environment Having selected the model architecture, open an draft PR to signal your intention to work on it. Follow the instructions below to set up your environment and open a draft PR. Fork the repository by clicking on the 'Fork' button on the repository's page. This creates a copy of the code under your GitHub user account. Clone your transformers fork to your local disk, and add the base repository as a remote: git clone https://github.com/[your Github handle]/transformers.git cd transformers git remote add upstream https://github.com/huggingface/transformers.git Set up a development environment, for instance by running the following command: python -m venv .env source .env/bin/activate pip install -e ".[dev]" Depending on your OS, and since the number of optional dependencies of Transformers is growing, you might get a failure with this command. If that's the case make sure to install TensorFlow then do: pip install -e ".[quality]" Note: You don't need to have CUDA installed. Making the new model work on CPU is sufficient. Create a branch with a descriptive name from your main branch git checkout -b add_tf_brand_new_bert Fetch and rebase to current main git fetch upstream git rebase upstream/main Add an empty .py file in transformers/src/models/brandnewbert/ named modeling_tf_brandnewbert.py. This will be your TensorFlow model file. Push the changes to your account using: git add . git commit -m "initial commit" git push -u origin add_tf_brand_new_bert Once you are satisfied, go to the webpage of your fork on GitHub. Click on “Pull request”. Make sure to add the GitHub handle of some members of the Hugging Face team as reviewers, so that the Hugging Face team gets notified for future changes. Change the PR into a draft by clicking on “Convert to draft” on the right of the GitHub pull request web page. Now you have set up a development environment to port BrandNewBert to TensorFlow in 🤗 Transformers. 3. (Optional) Understand theoretical aspects and the existing implementation You should take some time to read BrandNewBert's paper, if such descriptive work exists. There might be large sections of the paper that are difficult to understand. If this is the case, this is fine - don't worry! The goal is not to get a deep theoretical understanding of the paper, but to extract the necessary information required to effectively re-implement the model in 🤗 Transformers using TensorFlow. That being said, you don't have to spend too much time on the theoretical aspects, but rather focus on the practical ones, namely the existing model documentation page (e.g. model docs for BERT). After you've grasped the basics of the models you are about to implement, it's important to understand the existing implementation. This is a great chance to confirm that a working implementation matches your expectations for the model, as well as to foresee technical challenges on the TensorFlow side. It's perfectly natural that you feel overwhelmed with the amount of information that you've just absorbed. It is definitely not a requirement that you understand all facets of the model at this stage. Nevertheless, we highly encourage you to clear any pressing questions in our forum. 4. Model implementation Now it's time to finally start coding. Our suggested starting point is the PyTorch file itself: copy the contents of modeling_brand_new_bert.py inside src/transformers/models/brand_new_bert/ into modeling_tf_brand_new_bert.py. The goal of this section is to modify the file and update the import structure of 🤗 Transformers such that you can import TFBrandNewBert and TFBrandNewBert.from_pretrained(model_repo, from_pt=True) successfully loads a working TensorFlow BrandNewBert model. Sadly, there is no prescription to convert a PyTorch model into TensorFlow. You can, however, follow our selection of tips to make the process as smooth as possible: - Prepend TF to the name of all classes (e.g. BrandNewBert becomes TFBrandNewBert). - Most PyTorch operations have a direct TensorFlow replacement. For example, torch.nn.Linear corresponds to tf.keras.layers.Dense, torch.nn.Dropout corresponds to tf.keras.layers.Dropout, etc. If you're not sure about a specific operation, you can use the TensorFlow documentation or the PyTorch documentation. - Look for patterns in the 🤗 Transformers codebase. If you come across a certain operation that doesn't have a direct replacement, the odds are that someone else already had the same problem. - By default, keep the same variable names and structure as in PyTorch. This will make it easier to debug, track issues, and add fixes down the line. - Some layers have different default values in each framework. A notable example is the batch normalization layer's epsilon (1e-5 in PyTorch and 1e-3 in TensorFlow). Double-check the documentation! - PyTorch's nn.Parameter variables typically need to be initialized within TF Layer's build(). See the following example: PyTorch / TensorFlow - If the PyTorch model has a #copied from on top of a function, the odds are that your TensorFlow model can also borrow that function from the architecture it was copied from, assuming it has a TensorFlow architecture. - Assigning the name attribute correctly in TensorFlow functions is critical to do the from_pt=True weight cross-loading. name is almost always the name of the corresponding variable in the PyTorch code. If name is not properly set, you will see it in the error message when loading the model weights. - The logic of the base model class, BrandNewBertModel, will actually reside in TFBrandNewBertMainLayer, a Keras layer subclass (example). TFBrandNewBertModel will simply be a wrapper around this layer. - Keras models need to be built in order to load pretrained weights. For that reason, TFBrandNewBertPreTrainedModel will need to hold an example of inputs to the model, the dummy_inputs (example). - If you get stuck, ask for help - we're here to help you! 🤗 In addition to the model file itself, you will also need to add the pointers to the model classes and related documentation pages. You can complete this part entirely following the patterns in other PRs (example). Here's a list of the needed manual changes: - Include all public classes of BrandNewBert in src/transformers/__init__.py - Add BrandNewBert classes to the corresponding Auto classes in src/transformers/models/auto/modeling_tf_auto.py - Include the modeling file in the documentation test file list in utils/documentation_tests.txt - Add the lazy loading classes related to BrandNewBert in src/transformers/utils/dummy_tf_objects.py - Update the import structures for the public classes in src/transformers/models/brand_new_bert/__init__.py - Add the documentation pointers to the public methods of BrandNewBert in docs/source/en/model_doc/brand_new_bert.md - Add yourself to the list of contributors to BrandNewBert in docs/source/en/model_doc/brand_new_bert.md - Finally, add a green tick ✅ to the TensorFlow column of BrandNewBert in docs/source/en/index.md When you're happy with your implementation, run the following checklist to confirm that your model architecture is ready: 1. All layers that behave differently at train time (e.g. Dropout) are called with a training argument, which is propagated all the way from the top-level classes 2. You have used #copied from whenever possible 3. TFBrandNewBertMainLayer and all classes that use it have their call function decorated with @unpack_inputs 4. TFBrandNewBertMainLayer is decorated with @keras_serializable 5. A TensorFlow model can be loaded from PyTorch weights using TFBrandNewBert.from_pretrained(model_repo, from_pt=True) 6. You can call the TensorFlow model using the expected input format 5. Add model tests Hurray, you've implemented a TensorFlow model! Now it's time to add tests to make sure that your model behaves as expected. As in the previous section, we suggest you start by copying the test_modeling_brand_new_bert.py file in tests/models/brand_new_bert/ into test_modeling_tf_brand_new_bert.py, and continue by making the necessary TensorFlow replacements. For now, in all .from_pretrained() calls, you should use the from_pt=True flag to load the existing PyTorch weights. After you're done, it's time for the moment of truth: run the tests! 😬 NVIDIA_TF32_OVERRIDE=0 RUN_SLOW=1 RUN_PT_TF_CROSS_TESTS=1 \ py.test -vv tests/models/brand_new_bert/test_modeling_tf_brand_new_bert.py The most likely outcome is that you'll see a bunch of errors. Don't worry, this is expected! Debugging ML models is notoriously hard, and the key ingredient to success is patience (and breakpoint()). In our experience, the hardest problems arise from subtle mismatches between ML frameworks, for which we have a few pointers at the end of this guide. In other cases, a general test might not be directly applicable to your model, in which case we suggest an override at the model test class level. Regardless of the issue, don't hesitate to ask for help in your draft pull request if you're stuck. When all tests pass, congratulations, your model is nearly ready to be added to the 🤗 Transformers library! 🎉 6.-7. Ensure everyone can use your model 6. Submit the pull request Once you're done with the implementation and the tests, it's time to submit a pull request. Before pushing your code, run our code formatting utility, make fixup 🪄. This will automatically fix any formatting issues, which would cause our automatic checks to fail. It's now time to convert your draft pull request into a real pull request. To do so, click on the "Ready for review" button and add Joao (@gante) and Matt (@Rocketknight1) as reviewers. A model pull request will need at least 3 reviewers, but they will take care of finding appropriate additional reviewers for your model. After all reviewers are happy with the state of your PR, the final action point is to remove the from_pt=True flag in .from_pretrained() calls. Since there are no TensorFlow weights, you will have to add them! Check the section below for instructions on how to do it. Finally, when the TensorFlow weights get merged, you have at least 3 reviewer approvals, and all CI checks are green, double-check the tests locally one last time NVIDIA_TF32_OVERRIDE=0 RUN_SLOW=1 RUN_PT_TF_CROSS_TESTS=1 \ py.test -vv tests/models/brand_new_bert/test_modeling_tf_brand_new_bert.py and we will merge your PR! Congratulations on the milestone 🎉 7. (Optional) Build demos and share with the world One of the hardest parts about open-source is discovery. How can the other users learn about the existence of your fabulous TensorFlow contribution? With proper communication, of course! 📣 There are two main ways to share your model with the community: - Build demos. These include Gradio demos, notebooks, and other fun ways to show off your model. We highly encourage you to add a notebook to our community-driven demos. - Share stories on social media like Twitter and LinkedIn. You should be proud of your work and share your achievement with the community - your model can now be used by thousands of engineers and researchers around the world 🌍! We will be happy to retweet your posts and help you share your work with the community. Adding TensorFlow weights to 🤗 Hub Assuming that the TensorFlow model architecture is available in 🤗 Transformers, converting PyTorch weights into TensorFlow weights is a breeze! Here's how to do it: 1. Make sure you are logged into your Hugging Face account in your terminal. You can log in using the command huggingface-cli login (you can find your access tokens here) 2. Run transformers-cli pt-to-tf --model-name foo/bar, where foo/bar is the name of the model repository containing the PyTorch weights you want to convert 3. Tag @joaogante and @Rocketknight1 in the 🤗 Hub PR the command above has just created That's it! 🎉 Debugging mismatches across ML frameworks 🐛 At some point, when adding a new architecture or when creating TensorFlow weights for an existing architecture, you might come across errors compaining about mismatches between PyTorch and TensorFlow. You might even decide to open the model architecture code for the two frameworks, and find that they look identical. What's going on? 🤔 First of all, let's talk about why understanding these mismatches matters. Many community members will use 🤗 Transformers models out of the box, and trust that our models behave as expected. When there is a large mismatch between the two frameworks, it implies that the model is not following the reference implementation for at least one of the frameworks. This might lead to silent failures, in which the model runs but has poor performance. This is arguably worse than a model that fails to run at all! To that end, we aim at having a framework mismatch smaller than 1e-5 at all stages of the model. As in other numerical problems, the devil is in the details. And as in any detail-oriented craft, the secret ingredient here is patience. Here is our suggested workflow for when you come across this type of issues: 1. Locate the source of mismatches. The model you're converting probably has near identical inner variables up to a certain point. Place breakpoint() statements in the two frameworks' architectures, and compare the values of the numerical variables in a top-down fashion until you find the source of the problems. 2. Now that you've pinpointed the source of the issue, get in touch with the 🤗 Transformers team. It is possible that we've seen a similar problem before and can promptly provide a solution. As a fallback, scan popular pages like StackOverflow and GitHub issues. 3. If there is no solution in sight, it means you'll have to go deeper. The good news is that you've located the issue, so you can focus on the problematic instruction, abstracting away the rest of the model! The bad news is that you'll have to venture into the source implementation of said instruction. In some cases, you might find an issue with a reference implementation - don't abstain from opening an issue in the upstream repository. In some cases, in dicussion with the 🤗 Transformers team, we might find that the fixing the mismatch is infeasible. When the mismatch is very small in the output layers of the model (but potentially large in the hidden states), we might decide to ignore it in favor of distributing the model. The pt-to-tf CLI mentioned above has a --max-error flag to override the error message at weight conversion time.

Installation Install 🤗 Transformers for whichever deep learning library you're working with, setup your cache, and optionally configure 🤗 Transformers to run offline. 🤗 Transformers is tested on Python 3.6+, PyTorch 1.1.0+, TensorFlow 2.0+, and Flax. Follow the installation instructions below for the deep learning library you are using: PyTorch installation instructions. TensorFlow 2.0 installation instructions. Flax installation instructions. Install with pip You should install 🤗 Transformers in a virtual environment. If you're unfamiliar with Python virtual environments, take a look at this guide. A virtual environment makes it easier to manage different projects, and avoid compatibility issues between dependencies. Start by creating a virtual environment in your project directory: python -m venv .env Activate the virtual environment. On Linux and MacOs: source .env/bin/activate Activate Virtual environment on Windows .env/Scripts/activate Now you're ready to install 🤗 Transformers with the following command: pip install transformers For CPU-support only, you can conveniently install 🤗 Transformers and a deep learning library in one line. For example, install 🤗 Transformers and PyTorch with: pip install 'transformers[torch]' 🤗 Transformers and TensorFlow 2.0: pip install 'transformers[tf-cpu]' M1 / ARM Users You will need to install the following before installing TensorFLow 2.0 brew install cmake brew install pkg-config 🤗 Transformers and Flax: pip install 'transformers[flax]' Finally, check if 🤗 Transformers has been properly installed by running the following command. It will download a pretrained model: python -c "from transformers import pipeline; print(pipeline('sentiment-analysis')('we love you'))" Then print out the label and score: [{'label': 'POSITIVE', 'score': 0.9998704791069031}] Install from source Install 🤗 Transformers from source with the following command: pip install git+https://github.com/huggingface/transformers This command installs the bleeding edge main version rather than the latest stable version. The main version is useful for staying up-to-date with the latest developments. For instance, if a bug has been fixed since the last official release but a new release hasn't been rolled out yet. However, this means the main version may not always be stable. We strive to keep the main version operational, and most issues are usually resolved within a few hours or a day. If you run into a problem, please open an Issue so we can fix it even sooner! Check if 🤗 Transformers has been properly installed by running the following command: python -c "from transformers import pipeline; print(pipeline('sentiment-analysis')('I love you'))" Editable install You will need an editable install if you'd like to: Use the main version of the source code. Contribute to 🤗 Transformers and need to test changes in the code. Clone the repository and install 🤗 Transformers with the following commands: git clone https://github.com/huggingface/transformers.git cd transformers pip install -e . These commands will link the folder you cloned the repository to and your Python library paths. Python will now look inside the folder you cloned to in addition to the normal library paths. For example, if your Python packages are typically installed in ~/anaconda3/envs/main/lib/python3.7/site-packages/, Python will also search the folder you cloned to: ~/transformers/. You must keep the transformers folder if you want to keep using the library. Now you can easily update your clone to the latest version of 🤗 Transformers with the following command: cd ~/transformers/ git pull Your Python environment will find the main version of 🤗 Transformers on the next run. Install with conda Install from the conda channel huggingface: conda install -c huggingface transformers Cache setup Pretrained models are downloaded and locally cached at: ~/.cache/huggingface/hub. This is the default directory given by the shell environment variable TRANSFORMERS_CACHE. On Windows, the default directory is given by C:\Users\username\.cache\huggingface\hub. You can change the shell environment variables shown below - in order of priority - to specify a different cache directory: Shell environment variable (default): HUGGINGFACE_HUB_CACHE or TRANSFORMERS_CACHE. Shell environment variable: HF_HOME. Shell environment variable: XDG_CACHE_HOME + /huggingface. 🤗 Transformers will use the shell environment variables PYTORCH_TRANSFORMERS_CACHE or PYTORCH_PRETRAINED_BERT_CACHE if you are coming from an earlier iteration of this library and have set those environment variables, unless you specify the shell environment variable TRANSFORMERS_CACHE. Offline mode 🤗 Transformers is able to run in a firewalled or offline environment by only using local files. Set the environment variable TRANSFORMERS_OFFLINE=1 to enable this behavior. Add 🤗 Datasets to your offline training workflow by setting the environment variable HF_DATASETS_OFFLINE=1. For example, you would typically run a program on a normal network firewalled to external instances with the following command: python examples/pytorch/translation/run_translation.py --model_name_or_path t5-small --dataset_name wmt16 --dataset_config ro-en Run this same program in an offline instance with: HF_DATASETS_OFFLINE=1 TRANSFORMERS_OFFLINE=1 \ python examples/pytorch/translation/run_translation.py --model_name_or_path t5-small --dataset_name wmt16 --dataset_config ro-en The script should now run without hanging or waiting to timeout because it knows it should only look for local files. Fetch models and tokenizers to use offline Another option for using 🤗 Transformers offline is to download the files ahead of time, and then point to their local path when you need to use them offline. There are three ways to do this: Download a file through the user interface on the Model Hub by clicking on the ↓ icon. Use the [PreTrainedModel.from_pretrained] and [PreTrainedModel.save_pretrained] workflow: Download your files ahead of time with [PreTrainedModel.from_pretrained]: from transformers import AutoTokenizer, AutoModelForSeq2SeqLM tokenizer = AutoTokenizer.from_pretrained("bigscience/T0_3B") model = AutoModelForSeq2SeqLM.from_pretrained("bigscience/T0_3B") Save your files to a specified directory with [PreTrainedModel.save_pretrained]: tokenizer.save_pretrained("./your/path/bigscience_t0") model.save_pretrained("./your/path/bigscience_t0") Now when you're offline, reload your files with [PreTrainedModel.from_pretrained] from the specified directory: tokenizer = AutoTokenizer.from_pretrained("./your/path/bigscience_t0") model = AutoModel.from_pretrained("./your/path/bigscience_t0") Programmatically download files with the huggingface_hub library: Install the huggingface_hub library in your virtual environment: python -m pip install huggingface_hub Use the hf_hub_download function to download a file to a specific path. For example, the following command downloads the config.json file from the T0 model to your desired path: from huggingface_hub import hf_hub_download hf_hub_download(repo_id="bigscience/T0_3B", filename="config.json", cache_dir="./your/path/bigscience_t0") Once your file is downloaded and locally cached, specify it's local path to load and use it: from transformers import AutoConfig config = AutoConfig.from_pretrained("./your/path/bigscience_t0/config.json") See the How to download files from the Hub section for more details on downloading files stored on the Hub.

The Transformer model family Since its introduction in 2017, the original Transformer model has inspired many new and exciting models that extend beyond natural language processing (NLP) tasks. There are models for predicting the folded structure of proteins, training a cheetah to run, and time series forecasting. With so many Transformer variants available, it can be easy to miss the bigger picture. What all these models have in common is they're based on the original Transformer architecture. Some models only use the encoder or decoder, while others use both. This provides a useful taxonomy to categorize and examine the high-level differences within models in the Transformer family, and it'll help you understand Transformers you haven't encountered before. If you aren't familiar with the original Transformer model or need a refresher, check out the How do Transformers work chapter from the Hugging Face course. Computer vision Convolutional network For a long time, convolutional networks (CNNs) were the dominant paradigm for computer vision tasks until the Vision Transformer demonstrated its scalability and efficiency. Even then, some of a CNN's best qualities, like translation invariance, are so powerful (especially for certain tasks) that some Transformers incorporate convolutions in their architecture. ConvNeXt flipped this exchange around and incorporated design choices from Transformers to modernize a CNN. For example, ConvNeXt uses non-overlapping sliding windows to patchify an image and a larger kernel to increase its global receptive field. ConvNeXt also makes several layer design choices to be more memory-efficient and improve performance, so it competes favorably with Transformers! Encoder[[cv-encoder]] The Vision Transformer (ViT) opened the door to computer vision tasks without convolutions. ViT uses a standard Transformer encoder, but its main breakthrough was how it treated an image. It splits an image into fixed-size patches and uses them to create an embedding, just like how a sentence is split into tokens. ViT capitalized on the Transformers' efficient architecture to demonstrate competitive results with the CNNs at the time while requiring fewer resources to train. ViT was soon followed by other vision models that could also handle dense vision tasks like segmentation as well as detection. One of these models is the Swin Transformer. It builds hierarchical feature maps (like a CNN 👀 and unlike ViT) from smaller-sized patches and merges them with neighboring patches in deeper layers. Attention is only computed within a local window, and the window is shifted between attention layers to create connections to help the model learn better. Since the Swin Transformer can produce hierarchical feature maps, it is a good candidate for dense prediction tasks like segmentation and detection. The SegFormer also uses a Transformer encoder to build hierarchical feature maps, but it adds a simple multilayer perceptron (MLP) decoder on top to combine all the feature maps and make a prediction. Other vision models, like BeIT and ViTMAE, drew inspiration from BERT's pretraining objective. BeIT is pretrained by masked image modeling (MIM); the image patches are randomly masked, and the image is also tokenized into visual tokens. BeIT is trained to predict the visual tokens corresponding to the masked patches. ViTMAE has a similar pretraining objective, except it must predict the pixels instead of visual tokens. What's unusual is 75% of the image patches are masked! The decoder reconstructs the pixels from the masked tokens and encoded patches. After pretraining, the decoder is thrown away, and the encoder is ready to be used in downstream tasks. Decoder[[cv-decoder]] Decoder-only vision models are rare because most vision models rely on an encoder to learn an image representation. But for use cases like image generation, the decoder is a natural fit, as we've seen from text generation models like GPT-2. ImageGPT uses the same architecture as GPT-2, but instead of predicting the next token in a sequence, it predicts the next pixel in an image. In addition to image generation, ImageGPT could also be finetuned for image classification. Encoder-decoder[[cv-encoder-decoder]] Vision models commonly use an encoder (also known as a backbone) to extract important image features before passing them to a Transformer decoder. DETR has a pretrained backbone, but it also uses the complete Transformer encoder-decoder architecture for object detection. The encoder learns image representations and combines them with object queries (each object query is a learned embedding that focuses on a region or object in an image) in the decoder. DETR predicts the bounding box coordinates and class label for each object query. Natural language processing Encoder[[nlp-encoder]] BERT is an encoder-only Transformer that randomly masks certain tokens in the input to avoid seeing other tokens, which would allow it to "cheat". The pretraining objective is to predict the masked token based on the context. This allows BERT to fully use the left and right contexts to help it learn a deeper and richer representation of the inputs. However, there was still room for improvement in BERT's pretraining strategy. RoBERTa improved upon this by introducing a new pretraining recipe that includes training for longer and on larger batches, randomly masking tokens at each epoch instead of just once during preprocessing, and removing the next-sentence prediction objective. The dominant strategy to improve performance is to increase the model size. But training large models is computationally expensive. One way to reduce computational costs is using a smaller model like DistilBERT. DistilBERT uses knowledge distillation - a compression technique - to create a smaller version of BERT while keeping nearly all of its language understanding capabilities. However, most Transformer models continued to trend towards more parameters, leading to new models focused on improving training efficiency. ALBERT reduces memory consumption by lowering the number of parameters in two ways: separating the larger vocabulary embedding into two smaller matrices and allowing layers to share parameters. DeBERTa added a disentangled attention mechanism where the word and its position are separately encoded in two vectors. The attention is computed from these separate vectors instead of a single vector containing the word and position embeddings. Longformer also focused on making attention more efficient, especially for processing documents with longer sequence lengths. It uses a combination of local windowed attention (attention only calculated from fixed window size around each token) and global attention (only for specific task tokens like [CLS] for classification) to create a sparse attention matrix instead of a full attention matrix. Decoder[[nlp-decoder]] GPT-2 is a decoder-only Transformer that predicts the next word in the sequence. It masks tokens to the right so the model can't "cheat" by looking ahead. By pretraining on a massive body of text, GPT-2 became really good at generating text, even if the text is only sometimes accurate or true. But GPT-2 lacked the bidirectional context from BERT's pretraining, which made it unsuitable for certain tasks. XLNET combines the best of both BERT and GPT-2's pretraining objectives by using a permutation language modeling objective (PLM) that allows it to learn bidirectionally. After GPT-2, language models grew even bigger and are now known as large language models (LLMs). LLMs demonstrate few- or even zero-shot learning if pretrained on a large enough dataset. GPT-J is an LLM with 6B parameters and trained on 400B tokens. GPT-J was followed by OPT, a family of decoder-only models, the largest of which is 175B and trained on 180B tokens. BLOOM was released around the same time, and the largest model in the family has 176B parameters and is trained on 366B tokens in 46 languages and 13 programming languages. Encoder-decoder[[nlp-encoder-decoder]] BART keeps the original Transformer architecture, but it modifies the pretraining objective with text infilling corruption, where some text spans are replaced with a single mask token. The decoder predicts the uncorrupted tokens (future tokens are masked) and uses the encoder's hidden states to help it. Pegasus is similar to BART, but Pegasus masks entire sentences instead of text spans. In addition to masked language modeling, Pegasus is pretrained by gap sentence generation (GSG). The GSG objective masks whole sentences important to a document, replacing them with a mask token. The decoder must generate the output from the remaining sentences. T5 is a more unique model that casts all NLP tasks into a text-to-text problem using specific prefixes. For example, the prefix Summarize: indicates a summarization task. T5 is pretrained by supervised (GLUE and SuperGLUE) training and self-supervised training (randomly sample and drop out 15% of tokens). Audio Encoder[[audio-encoder]] Wav2Vec2 uses a Transformer encoder to learn speech representations directly from raw audio waveforms. It is pretrained with a contrastive task to determine the true speech representation from a set of false ones. HuBERT is similar to Wav2Vec2 but has a different training process. Target labels are created by a clustering step in which segments of similar audio are assigned to a cluster which becomes a hidden unit. The hidden unit is mapped to an embedding to make a prediction. Encoder-decoder[[audio-encoder-decoder]] Speech2Text is a speech model designed for automatic speech recognition (ASR) and speech translation. The model accepts log mel-filter bank features extracted from the audio waveform and pretrained autoregressively to generate a transcript or translation. Whisper is also an ASR model, but unlike many other speech models, it is pretrained on a massive amount of ✨ labeled ✨ audio transcription data for zero-shot performance. A large chunk of the dataset also contains non-English languages, meaning Whisper can also be used for low-resource languages. Structurally, Whisper is similar to Speech2Text. The audio signal is converted to a log-mel spectrogram encoded by the encoder. The decoder generates the transcript autoregressively from the encoder's hidden states and the previous tokens. Multimodal Encoder[[mm-encoder]] VisualBERT is a multimodal model for vision-language tasks released shortly after BERT. It combines BERT and a pretrained object detection system to extract image features into visual embeddings, passed alongside text embeddings to BERT. VisualBERT predicts the masked text based on the unmasked text and the visual embeddings, and it also has to predict whether the text is aligned with the image. When ViT was released, ViLT adopted ViT in its architecture because it was easier to get the image embeddings this way. The image embeddings are jointly processed with the text embeddings. From there, ViLT is pretrained by image text matching, masked language modeling, and whole word masking. CLIP takes a different approach and makes a pair prediction of (image, text) . An image encoder (ViT) and a text encoder (Transformer) are jointly trained on a 400 million (image, text) pair dataset to maximize the similarity between the image and text embeddings of the (image, text) pairs. After pretraining, you can use natural language to instruct CLIP to predict the text given an image or vice versa. OWL-ViT builds on top of CLIP by using it as its backbone for zero-shot object detection. After pretraining, an object detection head is added to make a set prediction over the (class, bounding box) pairs. Encoder-decoder[[mm-encoder-decoder]] Optical character recognition (OCR) is a long-standing text recognition task that typically involves several components to understand the image and generate the text. TrOCR simplifies the process using an end-to-end Transformer. The encoder is a ViT-style model for image understanding and processes the image as fixed-size patches. The decoder accepts the encoder's hidden states and autoregressively generates text. Donut is a more general visual document understanding model that doesn't rely on OCR-based approaches. It uses a Swin Transformer as the encoder and multilingual BART as the decoder. Donut is pretrained to read text by predicting the next word based on the image and text annotations. The decoder generates a token sequence given a prompt. The prompt is represented by a special token for each downstream task. For example, document parsing has a special parsing token that is combined with the encoder hidden states to parse the document into a structured output format (JSON). Reinforcement learning Decoder[[rl-decoder]] The Decision and Trajectory Transformer casts the state, action, and reward as a sequence modeling problem. The Decision Transformer generates a series of actions that lead to a future desired return based on returns-to-go, past states, and actions. For the last K timesteps, each of the three modalities are converted into token embeddings and processed by a GPT-like model to predict a future action token. Trajectory Transformer also tokenizes the states, actions, and rewards and processes them with a GPT architecture. Unlike the Decision Transformer, which is focused on reward conditioning, the Trajectory Transformer generates future actions with beam search.

Summary of the tokenizers [[open-in-colab]] On this page, we will have a closer look at tokenization. As we saw in the preprocessing tutorial, tokenizing a text is splitting it into words or subwords, which then are converted to ids through a look-up table. Converting words or subwords to ids is straightforward, so in this summary, we will focus on splitting a text into words or subwords (i.e. tokenizing a text). More specifically, we will look at the three main types of tokenizers used in 🤗 Transformers: Byte-Pair Encoding (BPE), WordPiece, and SentencePiece, and show examples of which tokenizer type is used by which model. Note that on each model page, you can look at the documentation of the associated tokenizer to know which tokenizer type was used by the pretrained model. For instance, if we look at [BertTokenizer], we can see that the model uses WordPiece. Introduction Splitting a text into smaller chunks is a task that is harder than it looks, and there are multiple ways of doing so. For instance, let's look at the sentence "Don't you love 🤗 Transformers? We sure do." A simple way of tokenizing this text is to split it by spaces, which would give: ["Don't", "you", "love", "🤗", "Transformers?", "We", "sure", "do."] This is a sensible first step, but if we look at the tokens "Transformers?" and "do.", we notice that the punctuation is attached to the words "Transformer" and "do", which is suboptimal. We should take the punctuation into account so that a model does not have to learn a different representation of a word and every possible punctuation symbol that could follow it, which would explode the number of representations the model has to learn. Taking punctuation into account, tokenizing our exemplary text would give: ["Don", "'", "t", "you", "love", "🤗", "Transformers", "?", "We", "sure", "do", "."] Better. However, it is disadvantageous, how the tokenization dealt with the word "Don't". "Don't" stands for "do not", so it would be better tokenized as ["Do", "n't"]. This is where things start getting complicated, and part of the reason each model has its own tokenizer type. Depending on the rules we apply for tokenizing a text, a different tokenized output is generated for the same text. A pretrained model only performs properly if you feed it an input that was tokenized with the same rules that were used to tokenize its training data. spaCy and Moses are two popular rule-based tokenizers. Applying them on our example, spaCy and Moses would output something like: ["Do", "n't", "you", "love", "🤗", "Transformers", "?", "We", "sure", "do", "."] As can be seen space and punctuation tokenization, as well as rule-based tokenization, is used here. Space and punctuation tokenization and rule-based tokenization are both examples of word tokenization, which is loosely defined as splitting sentences into words. While it's the most intuitive way to split texts into smaller chunks, this tokenization method can lead to problems for massive text corpora. In this case, space and punctuation tokenization usually generates a very big vocabulary (the set of all unique words and tokens used). E.g., Transformer XL uses space and punctuation tokenization, resulting in a vocabulary size of 267,735! Such a big vocabulary size forces the model to have an enormous embedding matrix as the input and output layer, which causes both an increased memory and time complexity. In general, transformers models rarely have a vocabulary size greater than 50,000, especially if they are pretrained only on a single language. So if simple space and punctuation tokenization is unsatisfactory, why not simply tokenize on characters? While character tokenization is very simple and would greatly reduce memory and time complexity it makes it much harder for the model to learn meaningful input representations. E.g. learning a meaningful context-independent representation for the letter "t" is much harder than learning a context-independent representation for the word "today". Therefore, character tokenization is often accompanied by a loss of performance. So to get the best of both worlds, transformers models use a hybrid between word-level and character-level tokenization called subword tokenization. Subword tokenization Subword tokenization algorithms rely on the principle that frequently used words should not be split into smaller subwords, but rare words should be decomposed into meaningful subwords. For instance "annoyingly" might be considered a rare word and could be decomposed into "annoying" and "ly". Both "annoying" and "ly" as stand-alone subwords would appear more frequently while at the same time the meaning of "annoyingly" is kept by the composite meaning of "annoying" and "ly". This is especially useful in agglutinative languages such as Turkish, where you can form (almost) arbitrarily long complex words by stringing together subwords. Subword tokenization allows the model to have a reasonable vocabulary size while being able to learn meaningful context-independent representations. In addition, subword tokenization enables the model to process words it has never seen before, by decomposing them into known subwords. For instance, the [~transformers.BertTokenizer] tokenizes "I have a new GPU!" as follows: from transformers import BertTokenizer tokenizer = BertTokenizer.from_pretrained("bert-base-uncased") tokenizer.tokenize("I have a new GPU!") ["i", "have", "a", "new", "gp", "##u", "!"] Because we are considering the uncased model, the sentence was lowercased first. We can see that the words ["i", "have", "a", "new"] are present in the tokenizer's vocabulary, but the word "gpu" is not. Consequently, the tokenizer splits "gpu" into known subwords: ["gp" and "##u"]. "##" means that the rest of the token should be attached to the previous one, without space (for decoding or reversal of the tokenization). As another example, [~transformers.XLNetTokenizer] tokenizes our previously exemplary text as follows: from transformers import XLNetTokenizer tokenizer = XLNetTokenizer.from_pretrained("xlnet-base-cased") tokenizer.tokenize("Don't you love 🤗 Transformers? We sure do.") ["▁Don", "'", "t", "▁you", "▁love", "▁", "🤗", "▁", "Transform", "ers", "?", "▁We", "▁sure", "▁do", "."] We'll get back to the meaning of those "▁" when we look at SentencePiece. As one can see, the rare word "Transformers" has been split into the more frequent subwords "Transform" and "ers". Let's now look at how the different subword tokenization algorithms work. Note that all of those tokenization algorithms rely on some form of training which is usually done on the corpus the corresponding model will be trained on. Byte-Pair Encoding (BPE) Byte-Pair Encoding (BPE) was introduced in Neural Machine Translation of Rare Words with Subword Units (Sennrich et al., 2015). BPE relies on a pre-tokenizer that splits the training data into words. Pretokenization can be as simple as space tokenization, e.g. GPT-2, Roberta. More advanced pre-tokenization include rule-based tokenization, e.g. XLM, FlauBERT which uses Moses for most languages, or GPT which uses Spacy and ftfy, to count the frequency of each word in the training corpus. After pre-tokenization, a set of unique words has been created and the frequency with which each word occurred in the training data has been determined. Next, BPE creates a base vocabulary consisting of all symbols that occur in the set of unique words and learns merge rules to form a new symbol from two symbols of the base vocabulary. It does so until the vocabulary has attained the desired vocabulary size. Note that the desired vocabulary size is a hyperparameter to define before training the tokenizer. As an example, let's assume that after pre-tokenization, the following set of words including their frequency has been determined: ("hug", 10), ("pug", 5), ("pun", 12), ("bun", 4), ("hugs", 5) Consequently, the base vocabulary is ["b", "g", "h", "n", "p", "s", "u"]. Splitting all words into symbols of the base vocabulary, we obtain: ("h" "u" "g", 10), ("p" "u" "g", 5), ("p" "u" "n", 12), ("b" "u" "n", 4), ("h" "u" "g" "s", 5) BPE then counts the frequency of each possible symbol pair and picks the symbol pair that occurs most frequently. In the example above "h" followed by "u" is present 10 + 5 = 15 times (10 times in the 10 occurrences of "hug", 5 times in the 5 occurrences of "hugs"). However, the most frequent symbol pair is "u" followed by "g", occurring 10 + 5 + 5 = 20 times in total. Thus, the first merge rule the tokenizer learns is to group all "u" symbols followed by a "g" symbol together. Next, "ug" is added to the vocabulary. The set of words then becomes ("h" "ug", 10), ("p" "ug", 5), ("p" "u" "n", 12), ("b" "u" "n", 4), ("h" "ug" "s", 5) BPE then identifies the next most common symbol pair. It's "u" followed by "n", which occurs 16 times. "u", "n" is merged to "un" and added to the vocabulary. The next most frequent symbol pair is "h" followed by "ug", occurring 15 times. Again the pair is merged and "hug" can be added to the vocabulary. At this stage, the vocabulary is ["b", "g", "h", "n", "p", "s", "u", "ug", "un", "hug"] and our set of unique words is represented as ("hug", 10), ("p" "ug", 5), ("p" "un", 12), ("b" "un", 4), ("hug" "s", 5) Assuming, that the Byte-Pair Encoding training would stop at this point, the learned merge rules would then be applied to new words (as long as those new words do not include symbols that were not in the base vocabulary). For instance, the word "bug" would be tokenized to ["b", "ug"] but "mug" would be tokenized as ["<unk>", "ug"] since the symbol "m" is not in the base vocabulary. In general, single letters such as "m" are not replaced by the "<unk>" symbol because the training data usually includes at least one occurrence of each letter, but it is likely to happen for very special characters like emojis. As mentioned earlier, the vocabulary size, i.e. the base vocabulary size + the number of merges, is a hyperparameter to choose. For instance GPT has a vocabulary size of 40,478 since they have 478 base characters and chose to stop training after 40,000 merges. Byte-level BPE A base vocabulary that includes all possible base characters can be quite large if e.g. all unicode characters are considered as base characters. To have a better base vocabulary, GPT-2 uses bytes as the base vocabulary, which is a clever trick to force the base vocabulary to be of size 256 while ensuring that every base character is included in the vocabulary. With some additional rules to deal with punctuation, the GPT2's tokenizer can tokenize every text without the need for the symbol. GPT-2 has a vocabulary size of 50,257, which corresponds to the 256 bytes base tokens, a special end-of-text token and the symbols learned with 50,000 merges. WordPiece WordPiece is the subword tokenization algorithm used for BERT, DistilBERT, and Electra. The algorithm was outlined in Japanese and Korean Voice Search (Schuster et al., 2012) and is very similar to BPE. WordPiece first initializes the vocabulary to include every character present in the training data and progressively learns a given number of merge rules. In contrast to BPE, WordPiece does not choose the most frequent symbol pair, but the one that maximizes the likelihood of the training data once added to the vocabulary. So what does this mean exactly? Referring to the previous example, maximizing the likelihood of the training data is equivalent to finding the symbol pair, whose probability divided by the probabilities of its first symbol followed by its second symbol is the greatest among all symbol pairs. E.g. "u", followed by "g" would have only been merged if the probability of "ug" divided by "u", "g" would have been greater than for any other symbol pair. Intuitively, WordPiece is slightly different to BPE in that it evaluates what it loses by merging two symbols to ensure it's worth it. Unigram Unigram is a subword tokenization algorithm introduced in Subword Regularization: Improving Neural Network Translation Models with Multiple Subword Candidates (Kudo, 2018). In contrast to BPE or WordPiece, Unigram initializes its base vocabulary to a large number of symbols and progressively trims down each symbol to obtain a smaller vocabulary. The base vocabulary could for instance correspond to all pre-tokenized words and the most common substrings. Unigram is not used directly for any of the models in the transformers, but it's used in conjunction with SentencePiece. At each training step, the Unigram algorithm defines a loss (often defined as the log-likelihood) over the training data given the current vocabulary and a unigram language model. Then, for each symbol in the vocabulary, the algorithm computes how much the overall loss would increase if the symbol was to be removed from the vocabulary. Unigram then removes p (with p usually being 10% or 20%) percent of the symbols whose loss increase is the lowest, i.e. those symbols that least affect the overall loss over the training data. This process is repeated until the vocabulary has reached the desired size. The Unigram algorithm always keeps the base characters so that any word can be tokenized. Because Unigram is not based on merge rules (in contrast to BPE and WordPiece), the algorithm has several ways of tokenizing new text after training. As an example, if a trained Unigram tokenizer exhibits the vocabulary: ["b", "g", "h", "n", "p", "s", "u", "ug", "un", "hug"], "hugs" could be tokenized both as ["hug", "s"], ["h", "ug", "s"] or ["h", "u", "g", "s"]. So which one to choose? Unigram saves the probability of each token in the training corpus on top of saving the vocabulary so that the probability of each possible tokenization can be computed after training. The algorithm simply picks the most likely tokenization in practice, but also offers the possibility to sample a possible tokenization according to their probabilities. Those probabilities are defined by the loss the tokenizer is trained on. Assuming that the training data consists of the words \(x_{1}, \dots, x_{N}\) and that the set of all possible tokenizations for a word \(x_{i}\) is defined as \(S(x_{i})\), then the overall loss is defined as $$\mathcal{L} = -\sum_{i=1}^{N} \log \left ( \sum_{x \in S(x_{i})} p(x) \right )$$ SentencePiece All tokenization algorithms described so far have the same problem: It is assumed that the input text uses spaces to separate words. However, not all languages use spaces to separate words. One possible solution is to use language specific pre-tokenizers, e.g. XLM uses a specific Chinese, Japanese, and Thai pre-tokenizer). To solve this problem more generally, SentencePiece: A simple and language independent subword tokenizer and detokenizer for Neural Text Processing (Kudo et al., 2018) treats the input as a raw input stream, thus including the space in the set of characters to use. It then uses the BPE or unigram algorithm to construct the appropriate vocabulary. The [XLNetTokenizer] uses SentencePiece for example, which is also why in the example earlier the "▁" character was included in the vocabulary. Decoding with SentencePiece is very easy since all tokens can just be concatenated and "▁" is replaced by a space. All transformers models in the library that use SentencePiece use it in combination with unigram. Examples of models using SentencePiece are ALBERT, XLNet, Marian, and T5.

Custom Tools and Prompts If you are not aware of what tools and agents are in the context of transformers, we recommend you read the Transformers Agents page first. Transformers Agent is an experimental API that is subject to change at any time. Results returned by the agents can vary as the APIs or underlying models are prone to change. Creating and using custom tools and prompts is paramount to empowering the agent and having it perform new tasks. In this guide we'll take a look at: How to customize the prompt How to use custom tools How to create custom tools Customizing the prompt As explained in Transformers Agents agents can run in [~Agent.run] and [~Agent.chat] mode. Both the run and chat modes underlie the same logic. The language model powering the agent is conditioned on a long prompt and completes the prompt by generating the next tokens until the stop token is reached. The only difference between the two modes is that during the chat mode the prompt is extended with previous user inputs and model generations. This allows the agent to have access to past interactions, seemingly giving the agent some kind of memory. Structure of the prompt Let's take a closer look at how the prompt is structured to understand how it can be best customized. The prompt is structured broadly into four parts. Introduction: how the agent should behave, explanation of the concept of tools. Description of all the tools. This is defined by a <<all_tools>> token that is dynamically replaced at runtime with the tools defined/chosen by the user. A set of examples of tasks and their solution Current example, and request for solution. To better understand each part, let's look at a shortened version of how the run prompt can look like: ````text I will ask you to perform a task, your job is to come up with a series of simple commands in Python that will perform the task. [] You can print intermediate results if it makes sense to do so. Tools: - document_qa: This is a tool that answers a question about a document (pdf). It takes an input named document which should be the document containing the information, as well as a question that is the question about the document. It returns a text that contains the answer to the question. - image_captioner: This is a tool that generates a description of an image. It takes an input named image which should be the image to the caption and returns a text that contains the description in English. [] Task: "Answer the question in the variable question about the image stored in the variable image. The question is in French." I will use the following tools: translator to translate the question into English and then image_qa to answer the question on the input image. Answer: py translated_question = translator(question=question, src_lang="French", tgt_lang="English") print(f"The translated question is {translated_question}.") answer = image_qa(image=image, question=translated_question) print(f"The answer is {answer}") Task: "Identify the oldest person in the document and create an image showcasing the result as a banner." I will use the following tools: document_qa to find the oldest person in the document, then image_generator to generate an image according to the answer. Answer: py answer = document_qa(document, question="What is the oldest person?") print(f"The answer is {answer}.") image = image_generator("A banner showing " + answer) [] Task: "Draw me a picture of rivers and lakes" I will use the following ` The introduction (the text before "Tools:") explains precisely how the model shall behave and what it should do. This part most likely does not need to be customized as the agent shall always behave the same way. The second part (the bullet points below "Tools") is dynamically added upon calling run or chat. There are exactly as many bullet points as there are tools in agent.toolbox and each bullet point consists of the name and description of the tool: text - <tool.name>: <tool.description> Let's verify this quickly by loading the document_qa tool and printing out the name and description. from transformers import load_tool document_qa = load_tool("document-question-answering") print(f"- {document_qa.name}: {document_qa.description}") which gives: text - document_qa: This is a tool that answers a question about a document (pdf). It takes an input named `document` which should be the document containing the information, as well as a `question` that is the question about the document. It returns a text that contains the answer to the question. We can see that the tool name is short and precise. The description includes two parts, the first explaining what the tool does and the second states what input arguments and return values are expected. A good tool name and tool description are very important for the agent to correctly use it. Note that the only information the agent has about the tool is its name and description, so one should make sure that both are precisely written and match the style of the existing tools in the toolbox. In particular make sure the description mentions all the arguments expected by name in code-style, along with the expected type and a description of what they are. Check the naming and description of the curated Transformers tools to better understand what name and description a tool is expected to have. You can see all tools with the [Agent.toolbox] property. The third part includes a set of curated examples that show the agent exactly what code it should produce for what kind of user request. The large language models empowering the agent are extremely good at recognizing patterns in a prompt and repeating the pattern with new data. Therefore, it is very important that the examples are written in a way that maximizes the likelihood of the agent to generating correct, executable code in practice. Let's have a look at one example: ```text Task: "Identify the oldest person in thedocument` and create an image showcasing the result as a banner." I will use the following tools: document_qa to find the oldest person in the document, then image_generator to generate an image according to the answer. Answer: py answer = document_qa(document, question="What is the oldest person?") print(f"The answer is {answer}.") image = image_generator("A banner showing " + answer) ` The pattern the model is prompted to repeat has three parts: The task statement, the agent's explanation of what it intends to do, and finally the generated code. Every example that is part of the prompt has this exact pattern, thus making sure that the agent will reproduce exactly the same pattern when generating new tokens. The prompt examples are curated by the Transformers team and rigorously evaluated on a set of problem statements to ensure that the agent's prompt is as good as possible to solve real use cases of the agent. The final part of the prompt corresponds to: ```text Task: "Draw me a picture of rivers and lakes" I will use the following is a final and unfinished example that the agent is tasked to complete. The unfinished example is dynamically created based on the actual user input. For the above example, the user ran: py agent.run("Draw me a picture of rivers and lakes") The user input - a.k.a the task: "Draw me a picture of rivers and lakes" is cast into the prompt template: "Task: \n\n I will use the following". This sentence makes up the final lines of the prompt the agent is conditioned on, therefore strongly influencing the agent to finish the example exactly in the same way it was previously done in the examples. Without going into too much detail, the chat template has the same prompt structure with the examples having a slightly different style, e.g.: ````text [] ===== Human: Answer the question in the variable question about the image stored in the variable image. Assistant: I will use the tool image_qa to answer the question on the input image. py answer = image_qa(text=question, image=image) print(f"The answer is {answer}") Human: I tried this code, it worked but didn't give me a good result. The question is in French Assistant: In this case, the question needs to be translated first. I will use the tool translator to do this. py translated_question = translator(question=question, src_lang="French", tgt_lang="English") print(f"The translated question is {translated_question}.") answer = image_qa(text=translated_question, image=image) print(f"The answer is {answer}") ===== [] ` Contrary, to the examples of the run prompt, each chat prompt example has one or more exchanges between the Human and the Assistant. Every exchange is structured similarly to the example of the run prompt. The user's input is appended to behind Human: and the agent is prompted to first generate what needs to be done before generating code. An exchange can be based on previous exchanges, therefore allowing the user to refer to past exchanges as is done e.g. above by the user's input of "I tried this code" refers to the previously generated code of the agent. Upon running .chat, the user's input or task is cast into an unfinished example of the form: text Human: <user-input>\n\nAssistant: which the agent completes. Contrary to the run command, the chat command then appends the completed example to the prompt, thus giving the agent more context for the next chat turn. Great now that we know how the prompt is structured, let's see how we can customize it! Writing good user inputs While large language models are getting better and better at understanding users' intentions, it helps enormously to be as precise as possible to help the agent pick the correct task. What does it mean to be as precise as possible? The agent sees a list of tool names and their description in its prompt. The more tools are added the more difficult it becomes for the agent to choose the correct tool and it's even more difficult to choose the correct sequences of tools to run. Let's look at a common failure case, here we will only return the code to analyze it. from transformers import HfAgent agent = HfAgent("https://api-inference.huggingface.co/models/bigcode/starcoder") agent.run("Show me a tree", return_code=True) gives: ``text ==Explanation from the agent== I will use the following tool:image_segmenter` to create a segmentation mask for the image. ==Code generated by the agent== mask = image_segmenter(image, prompt="tree") which is probably not what we wanted. Instead, it is more likely that we want an image of a tree to be generated. To steer the agent more towards using a specific tool it can therefore be very helpful to use important keywords that are present in the tool's name and description. Let's have a look. py agent.toolbox["image_generator"].description text 'This is a tool that creates an image according to a prompt, which is a text description. It takes an input named `prompt` which contains the image description and outputs an image. The name and description make use of the keywords "image", "prompt", "create" and "generate". Using these words will most likely work better here. Let's refine our prompt a bit. py agent.run("Create an image of a tree", return_code=True) gives: ``text ==Explanation from the agent== I will use the following toolimage_generator` to generate an image of a tree. ==Code generated by the agent== image = image_generator(prompt="tree") Much better! That looks more like what we want. In short, when you notice that the agent struggles to correctly map your task to the correct tools, try looking up the most pertinent keywords of the tool's name and description and try refining your task request with it. Customizing the tool descriptions As we've seen before the agent has access to each of the tools' names and descriptions. The base tools should have very precise names and descriptions, however, you might find that it could help to change the the description or name of a tool for your specific use case. This might become especially important when you've added multiple tools that are very similar or if you want to use your agent only for a certain domain, e.g. image generation and transformations. A common problem is that the agent confuses image generation with image transformation/modification when used a lot for image generation tasks, e.g. py agent.run("Make an image of a house and a car", return_code=True) returns ``text ==Explanation from the agent== I will use the following toolsimage_generatorto generate an image of a house andimage_transformer` to transform the image of a car into the image of a house. ==Code generated by the agent== house_image = image_generator(prompt="A house") car_image = image_generator(prompt="A car") house_car_image = image_transformer(image=car_image, prompt="A house") which is probably not exactly what we want here. It seems like the agent has a difficult time to understand the difference between image_generator and image_transformer and often uses the two together. We can help the agent here by changing the tool name and description of image_transformer. Let's instead call it modifier to disassociate it a bit from "image" and "prompt": py agent.toolbox["modifier"] = agent.toolbox.pop("image_transformer") agent.toolbox["modifier"].description = agent.toolbox["modifier"].description.replace( "transforms an image according to a prompt", "modifies an image" ) Now "modify" is a strong cue to use the new image processor which should help with the above prompt. Let's run it again. py agent.run("Make an image of a house and a car", return_code=True) Now we're getting: ``text ==Explanation from the agent== I will use the following tools:image_generatorto generate an image of a house, thenimage_generator` to generate an image of a car. ==Code generated by the agent== house_image = image_generator(prompt="A house") car_image = image_generator(prompt="A car") which is definitely closer to what we had in mind! However, we want to have both the house and car in the same image. Steering the task more toward single image generation should help: py agent.run("Create image: 'A house and car'", return_code=True) ``text ==Explanation from the agent== I will use the following tool:image_generator` to generate an image. ==Code generated by the agent== image = image_generator(prompt="A house and car") Agents are still brittle for many use cases, especially when it comes to slightly more complex use cases like generating an image of multiple objects. Both the agent itself and the underlying prompt will be further improved in the coming months making sure that agents become more robust to a variety of user inputs. Customizing the whole prompt To give the user maximum flexibility, the whole prompt template as explained in above can be overwritten by the user. In this case make sure that your custom prompt includes an introduction section, a tool section, an example section, and an unfinished example section. If you want to overwrite the run prompt template, you can do as follows: template = """ [] """ agent = HfAgent(your_endpoint, run_prompt_template=template) Please make sure to have the <<all_tools>> string and the <<prompt>> defined somewhere in the template so that the agent can be aware of the tools, it has available to it as well as correctly insert the user's prompt. Similarly, one can overwrite the chat prompt template. Note that the chat mode always uses the following format for the exchanges: ```text Human: <> Assistant: Therefore it is important that the examples of the custom chat prompt template also make use of this format. You can overwrite the chat template at instantiation as follows. template = """ [] """ agent = HfAgent(url_endpoint=your_endpoint, chat_prompt_template=template) Please make sure to have the <<all_tools>> string defined somewhere in the template so that the agent can be aware of the tools, it has available to it. In both cases, you can pass a repo ID instead of the prompt template if you would like to use a template hosted by someone in the community. The default prompts live in this repo as an example. To upload your custom prompt on a repo on the Hub and share it with the community just make sure: - to use a dataset repository - to put the prompt template for the run command in a file named run_prompt_template.txt - to put the prompt template for the chat command in a file named chat_prompt_template.txt Using custom tools In this section, we'll be leveraging two existing custom tools that are specific to image generation: We replace huggingface-tools/image-transformation, with diffusers/controlnet-canny-tool to allow for more image modifications. We add a new tool for image upscaling to the default toolbox: diffusers/latent-upscaler-tool replace the existing image-transformation tool. We'll start by loading the custom tools with the convenient [load_tool] function: from transformers import load_tool controlnet_transformer = load_tool("diffusers/controlnet-canny-tool") upscaler = load_tool("diffusers/latent-upscaler-tool") Upon adding custom tools to an agent, the tools' descriptions and names are automatically included in the agents' prompts. Thus, it is imperative that custom tools have a well-written description and name in order for the agent to understand how to use them. Let's take a look at the description and name of controlnet_transformer: py print(f"Description: '{controlnet_transformer.description}'") print(f"Name: '{controlnet_transformer.name}'") gives text Description: 'This is a tool that transforms an image with ControlNet according to a prompt. It takes two inputs: `image`, which should be the image to transform, and `prompt`, which should be the prompt to use to change it. It returns the modified image.' Name: 'image_transformer' The name and description are accurate and fit the style of the curated set of tools. Next, let's instantiate an agent with controlnet_transformer and upscaler: py tools = [controlnet_transformer, upscaler] agent = HfAgent("https://api-inference.huggingface.co/models/bigcode/starcoder", additional_tools=tools) This command should give you the following info: text image_transformer has been replaced by <transformers_modules.diffusers.controlnet-canny-tool.bd76182c7777eba9612fc03c0 8718a60c0aa6312.image_transformation.ControlNetTransformationTool object at 0x7f1d3bfa3a00> as provided in `additional_tools` The set of curated tools already has an image_transformer tool which is hereby replaced with our custom tool. Overwriting existing tools can be beneficial if we want to use a custom tool exactly for the same task as an existing tool because the agent is well-versed in using the specific task. Beware that the custom tool should follow the exact same API as the overwritten tool in this case, or you should adapt the prompt template to make sure all examples using that tool are updated. The upscaler tool was given the name image_upscaler which is not yet present in the default toolbox and is therefore simply added to the list of tools. You can always have a look at the toolbox that is currently available to the agent via the agent.toolbox attribute: py print("\n".join([f"- {a}" for a in agent.toolbox.keys()])) text - document_qa - image_captioner - image_qa - image_segmenter - transcriber - summarizer - text_classifier - text_qa - text_reader - translator - image_transformer - text_downloader - image_generator - video_generator - image_upscaler Note how image_upscaler is now part of the agents' toolbox. Let's now try out the new tools! We will re-use the image we generated in Transformers Agents Quickstart. from diffusers.utils import load_image image = load_image( "https://huggingface.co./datasets/huggingface/documentation-images/resolve/main/transformers/rivers_and_lakes.png" ) Let's transform the image into a beautiful winter landscape: py image = agent.run("Transform the image: 'A frozen lake and snowy forest'", image=image) ``text ==Explanation from the agent== I will use the following tool:image_transformer` to transform the image. ==Code generated by the agent== image = image_transformer(image, prompt="A frozen lake and snowy forest") The new image processing tool is based on ControlNet which can make very strong modifications to the image. By default the image processing tool returns an image of size 512x512 pixels. Let's see if we can upscale it. py image = agent.run("Upscale the image", image) ``text ==Explanation from the agent== I will use the following tool:image_upscaler` to upscale the image. ==Code generated by the agent== upscaled_image = image_upscaler(image) The agent automatically mapped our prompt "Upscale the image" to the just added upscaler tool purely based on the description and name of the upscaler tool and was able to correctly run it. Next, let's have a look at how you can create a new custom tool. Adding new tools In this section, we show how to create a new tool that can be added to the agent. Creating a new tool We'll first start by creating a tool. We'll add the not-so-useful yet fun task of fetching the model on the Hugging Face Hub with the most downloads for a given task. We can do that with the following code: thon from huggingface_hub import list_models task = "text-classification" model = next(iter(list_models(filter=task, sort="downloads", direction=-1))) print(model.id) For the task text-classification, this returns 'facebook/bart-large-mnli', for translation it returns 't5-base. How do we convert this to a tool that the agent can leverage? All tools depend on the superclass Tool that holds the main attributes necessary. We'll create a class that inherits from it: thon from transformers import Tool class HFModelDownloadsTool(Tool): pass This class has a few needs: - An attribute name, which corresponds to the name of the tool itself. To be in tune with other tools which have a performative name, we'll name it model_download_counter. - An attribute description, which will be used to populate the prompt of the agent. - inputs and outputs attributes. Defining this will help the python interpreter make educated choices about types, and will allow for a gradio-demo to be spawned when we push our tool to the Hub. They're both a list of expected values, which can be text, image, or audio. - A __call__ method which contains the inference code. This is the code we've played with above! Here's what our class looks like now: thon from transformers import Tool from huggingface_hub import list_models class HFModelDownloadsTool(Tool): name = "model_download_counter" description = ( "This is a tool that returns the most downloaded model of a given task on the Hugging Face Hub. " "It takes the name of the category (such as text-classification, depth-estimation, etc), and " "returns the name of the checkpoint." ) inputs = ["text"] outputs = ["text"] def __call__(self, task: str): model = next(iter(list_models(filter=task, sort="downloads", direction=-1))) return model.id We now have our tool handy. Save it in a file and import it from your main script. Let's name this file model_downloads.py, so the resulting import code looks like this: thon from model_downloads import HFModelDownloadsTool tool = HFModelDownloadsTool() In order to let others benefit from it and for simpler initialization, we recommend pushing it to the Hub under your namespace. To do so, just call push_to_hub on the tool variable: python tool.push_to_hub("hf-model-downloads") You now have your code on the Hub! Let's take a look at the final step, which is to have the agent use it. Having the agent use the tool We now have our tool that lives on the Hub which can be instantiated as such (change the user name for your tool): thon from transformers import load_tool tool = load_tool("lysandre/hf-model-downloads") In order to use it in the agent, simply pass it in the additional_tools parameter of the agent initialization method: thon from transformers import HfAgent agent = HfAgent("https://api-inference.huggingface.co/models/bigcode/starcoder", additional_tools=[tool]) agent.run( "Can you read out loud the name of the model that has the most downloads in the 'text-to-video' task on the Hugging Face Hub?" ) which outputs the following:text ==Code generated by the agent== model = model_download_counter(task="text-to-video") print(f"The model with the most downloads is {model}.") audio_model = text_reader(model) ==Result== The model with the most downloads is damo-vilab/text-to-video-ms-1.7b. and generates the following audio. | Audio | |------------------------------------------------------------------------------------------------------------------------------------------------------| | | Depending on the LLM, some are quite brittle and require very exact prompts in order to work well. Having a well-defined name and description of the tool is paramount to having it be leveraged by the agent. Replacing existing tools Replacing existing tools can be done simply by assigning a new item to the agent's toolbox. Here's how one would do so: thon from transformers import HfAgent, load_tool agent = HfAgent("https://api-inference.huggingface.co/models/bigcode/starcoder") agent.toolbox["image-transformation"] = load_tool("diffusers/controlnet-canny-tool") Beware when replacing tools with others! This will also adjust the agent's prompt. This can be good if you have a better prompt suited for the task, but it can also result in your tool being selected way more than others or for other tools to be selected instead of the one you have defined. Leveraging gradio-tools gradio-tools is a powerful library that allows using Hugging Face Spaces as tools. It supports many existing Spaces as well as custom Spaces to be designed with it. We offer support for gradio_tools by using the Tool.from_gradio method. For example, we want to take advantage of the StableDiffusionPromptGeneratorTool tool offered in the gradio-tools toolkit so as to improve our prompts and generate better images. We first import the tool from gradio_tools and instantiate it: thon from gradio_tools import StableDiffusionPromptGeneratorTool gradio_tool = StableDiffusionPromptGeneratorTool() We pass that instance to the Tool.from_gradio method: thon from transformers import Tool tool = Tool.from_gradio(gradio_tool) Now we can manage it exactly as we would a usual custom tool. We leverage it to improve our prompt a rabbit wearing a space suit: thon from transformers import HfAgent agent = HfAgent("https://api-inference.huggingface.co/models/bigcode/starcoder", additional_tools=[tool]) agent.run("Generate an image of the prompt after improving it.", prompt="A rabbit wearing a space suit") The model adequately leverages the tool: ``text ==Explanation from the agent== I will use the following tools:StableDiffusionPromptGeneratorto improve the prompt, thenimage_generator` to generate an image according to the improved prompt. ==Code generated by the agent== improved_prompt = StableDiffusionPromptGenerator(prompt) print(f"The improved prompt is {improved_prompt}.") image = image_generator(improved_prompt) Before finally generating the image: gradio-tools requires textual inputs and outputs, even when working with different modalities. This implementation works with image and audio objects. The two are currently incompatible, but will rapidly become compatible as we work to improve the support. Future compatibility with Langchain We love Langchain and think it has a very compelling suite of tools. In order to handle these tools, Langchain requires textual inputs and outputs, even when working with different modalities. This is often the serialized version (i.e., saved to disk) of the objects. This difference means that multi-modality isn't handled between transformers-agents and langchain. We aim for this limitation to be resolved in future versions, and welcome any help from avid langchain users to help us achieve this compatibility. We would love to have better support. If you would like to help, please open an issue and share what you have in mind.

Custom hardware for training The hardware you use to run model training and inference can have a big effect on performance. For a deep dive into GPUs make sure to check out Tim Dettmer's excellent blog post. Let's have a look at some practical advice for GPU setups. GPU When you train bigger models you have essentially three options: - bigger GPUs - more GPUs - more CPU and NVMe (offloaded to by DeepSpeed-Infinity) Let's start at the case where you have a single GPU. Power and Cooling If you bought an expensive high end GPU make sure you give it the correct power and sufficient cooling. Power: Some high end consumer GPU cards have 2 and sometimes 3 PCI-E 8-Pin power sockets. Make sure you have as many independent 12V PCI-E 8-Pin cables plugged into the card as there are sockets. Do not use the 2 splits at one end of the same cable (also known as pigtail cable). That is if you have 2 sockets on the GPU, you want 2 PCI-E 8-Pin cables going from your PSU to the card and not one that has 2 PCI-E 8-Pin connectors at the end! You won't get the full performance out of your card otherwise. Each PCI-E 8-Pin power cable needs to be plugged into a 12V rail on the PSU side and can supply up to 150W of power. Some other cards may use a PCI-E 12-Pin connectors, and these can deliver up to 500-600W of power. Low end cards may use 6-Pin connectors, which supply up to 75W of power. Additionally you want the high-end PSU that has stable voltage. Some lower quality ones may not give the card the stable voltage it needs to function at its peak. And of course the PSU needs to have enough unused Watts to power the card. Cooling: When a GPU gets overheated it will start throttling down and will not deliver full performance and it can even shutdown if it gets too hot. It's hard to tell the exact best temperature to strive for when a GPU is heavily loaded, but probably anything under +80C is good, but lower is better - perhaps 70-75C is an excellent range to be in. The throttling down is likely to start at around 84-90C. But other than throttling performance a prolonged very high temperature is likely to reduce the lifespan of a GPU. Next let's have a look at one of the most important aspects when having multiple GPUs: connectivity. Multi-GPU Connectivity If you use multiple GPUs the way cards are inter-connected can have a huge impact on the total training time. If the GPUs are on the same physical node, you can run: nvidia-smi topo -m and it will tell you how the GPUs are inter-connected. On a machine with dual-GPU and which are connected with NVLink, you will most likely see something like: GPU0 GPU1 CPU Affinity NUMA Affinity GPU0 X NV2 0-23 N/A GPU1 NV2 X 0-23 N/A on a different machine w/o NVLink we may see: GPU0 GPU1 CPU Affinity NUMA Affinity GPU0 X PHB 0-11 N/A GPU1 PHB X 0-11 N/A The report includes this legend: X = Self SYS = Connection traversing PCIe as well as the SMP interconnect between NUMA nodes (e.g., QPI/UPI) NODE = Connection traversing PCIe as well as the interconnect between PCIe Host Bridges within a NUMA node PHB = Connection traversing PCIe as well as a PCIe Host Bridge (typically the CPU) PXB = Connection traversing multiple PCIe bridges (without traversing the PCIe Host Bridge) PIX = Connection traversing at most a single PCIe bridge NV# = Connection traversing a bonded set of # NVLinks So the first report NV2 tells us the GPUs are interconnected with 2 NVLinks, and the second report PHB we have a typical consumer-level PCIe+Bridge setup. Check what type of connectivity you have on your setup. Some of these will make the communication between cards faster (e.g. NVLink), others slower (e.g. PHB). Depending on the type of scalability solution used, the connectivity speed could have a major or a minor impact. If the GPUs need to sync rarely, as in DDP, the impact of a slower connection will be less significant. If the GPUs need to send messages to each other often, as in ZeRO-DP, then faster connectivity becomes super important to achieve faster training. NVlink NVLink is a wire-based serial multi-lane near-range communications link developed by Nvidia. Each new generation provides a faster bandwidth, e.g. here is a quote from Nvidia Ampere GA102 GPU Architecture: Third-Generation NVLink® GA102 GPUs utilize NVIDIA’s third-generation NVLink interface, which includes four x4 links, with each link providing 14.0625 GB/sec bandwidth in each direction between two GPUs. Four links provide 56.25 GB/sec bandwidth in each direction, and 112.5 GB/sec total bandwidth between two GPUs. Two RTX 3090 GPUs can be connected together for SLI using NVLink. (Note that 3-Way and 4-Way SLI configurations are not supported.) So the higher X you get in the report of NVX in the output of nvidia-smi topo -m the better. The generation will depend on your GPU architecture. Let's compare the execution of a gpt2 language model training over a small sample of wikitext. The results are: | NVlink | Time | | ----- | ---: | | Y | 101s | | N | 131s | You can see that NVLink completes the training ~23% faster. In the second benchmark we use NCCL_P2P_DISABLE=1 to tell the GPUs not to use NVLink. Here is the full benchmark code and outputs: ```bash DDP w/ NVLink rm -r /tmp/test-clm; CUDA_VISIBLE_DEVICES=0,1 python -m torch.distributed.launch \ --nproc_per_node 2 examples/pytorch/language-modeling/run_clm.py --model_name_or_path gpt2 \ --dataset_name wikitext --dataset_config_name wikitext-2-raw-v1 --do_train \ --output_dir /tmp/test-clm --per_device_train_batch_size 4 --max_steps 200 {'train_runtime': 101.9003, 'train_samples_per_second': 1.963, 'epoch': 0.69} DDP w/o NVLink rm -r /tmp/test-clm; CUDA_VISIBLE_DEVICES=0,1 NCCL_P2P_DISABLE=1 python -m torch.distributed.launch \ --nproc_per_node 2 examples/pytorch/language-modeling/run_clm.py --model_name_or_path gpt2 \ --dataset_name wikitext --dataset_config_name wikitext-2-raw-v1 --do_train --output_dir /tmp/test-clm --per_device_train_batch_size 4 --max_steps 200 {'train_runtime': 131.4367, 'train_samples_per_second': 1.522, 'epoch': 0.69} Hardware: 2x TITAN RTX 24GB each + NVlink with 2 NVLinks (NV2 in nvidia-smi topo -m) Software: pytorch-1.8-to-be + cuda-11.0 / transformers==4.3.0.dev0

Multilingual models for inference [[open-in-colab]] There are several multilingual models in 🤗 Transformers, and their inference usage differs from monolingual models. Not all multilingual model usage is different though. Some models, like bert-base-multilingual-uncased, can be used just like a monolingual model. This guide will show you how to use multilingual models whose usage differs for inference. XLM XLM has ten different checkpoints, only one of which is monolingual. The nine remaining model checkpoints can be split into two categories: the checkpoints that use language embeddings and those that don't. XLM with language embeddings The following XLM models use language embeddings to specify the language used at inference: xlm-mlm-ende-1024 (Masked language modeling, English-German) xlm-mlm-enfr-1024 (Masked language modeling, English-French) xlm-mlm-enro-1024 (Masked language modeling, English-Romanian) xlm-mlm-xnli15-1024 (Masked language modeling, XNLI languages) xlm-mlm-tlm-xnli15-1024 (Masked language modeling + translation, XNLI languages) xlm-clm-enfr-1024 (Causal language modeling, English-French) xlm-clm-ende-1024 (Causal language modeling, English-German) Language embeddings are represented as a tensor of the same shape as the input_ids passed to the model. The values in these tensors depend on the language used and are identified by the tokenizer's lang2id and id2lang attributes. In this example, load the xlm-clm-enfr-1024 checkpoint (Causal language modeling, English-French): import torch from transformers import XLMTokenizer, XLMWithLMHeadModel tokenizer = XLMTokenizer.from_pretrained("xlm-clm-enfr-1024") model = XLMWithLMHeadModel.from_pretrained("xlm-clm-enfr-1024") The lang2id attribute of the tokenizer displays this model's languages and their ids: print(tokenizer.lang2id) {'en': 0, 'fr': 1} Next, create an example input: input_ids = torch.tensor([tokenizer.encode("Wikipedia was used to")]) # batch size of 1 Set the language id as "en" and use it to define the language embedding. The language embedding is a tensor filled with 0 since that is the language id for English. This tensor should be the same size as input_ids. language_id = tokenizer.lang2id["en"] # 0 langs = torch.tensor([language_id] * input_ids.shape[1]) # torch.tensor([0, 0, 0, , 0]) We reshape it to be of size (batch_size, sequence_length) langs = langs.view(1, -1) # is now of shape [1, sequence_length] (we have a batch size of 1) Now you can pass the input_ids and language embedding to the model: outputs = model(input_ids, langs=langs) The run_generation.py script can generate text with language embeddings using the xlm-clm checkpoints. XLM without language embeddings The following XLM models do not require language embeddings during inference: xlm-mlm-17-1280 (Masked language modeling, 17 languages) xlm-mlm-100-1280 (Masked language modeling, 100 languages) These models are used for generic sentence representations, unlike the previous XLM checkpoints. BERT The following BERT models can be used for multilingual tasks: bert-base-multilingual-uncased (Masked language modeling + Next sentence prediction, 102 languages) bert-base-multilingual-cased (Masked language modeling + Next sentence prediction, 104 languages) These models do not require language embeddings during inference. They should identify the language from the context and infer accordingly. XLM-RoBERTa The following XLM-RoBERTa models can be used for multilingual tasks: xlm-roberta-base (Masked language modeling, 100 languages) xlm-roberta-large (Masked language modeling, 100 languages) XLM-RoBERTa was trained on 2.5TB of newly created and cleaned CommonCrawl data in 100 languages. It provides strong gains over previously released multilingual models like mBERT or XLM on downstream tasks like classification, sequence labeling, and question answering. M2M100 The following M2M100 models can be used for multilingual translation: facebook/m2m100_418M (Translation) facebook/m2m100_1.2B (Translation) In this example, load the facebook/m2m100_418M checkpoint to translate from Chinese to English. You can set the source language in the tokenizer: from transformers import M2M100ForConditionalGeneration, M2M100Tokenizer en_text = "Do not meddle in the affairs of wizards, for they are subtle and quick to anger." chinese_text = "不要插手巫師的事務, 因為他們是微妙的, 很快就會發怒." tokenizer = M2M100Tokenizer.from_pretrained("facebook/m2m100_418M", src_lang="zh") model = M2M100ForConditionalGeneration.from_pretrained("facebook/m2m100_418M") Tokenize the text: encoded_zh = tokenizer(chinese_text, return_tensors="pt") M2M100 forces the target language id as the first generated token to translate to the target language. Set the forced_bos_token_id to en in the generate method to translate to English: generated_tokens = model.generate(**encoded_zh, forced_bos_token_id=tokenizer.get_lang_id("en")) tokenizer.batch_decode(generated_tokens, skip_special_tokens=True) 'Do not interfere with the matters of the witches, because they are delicate and will soon be angry.' MBart The following MBart models can be used for multilingual translation: facebook/mbart-large-50-one-to-many-mmt (One-to-many multilingual machine translation, 50 languages) facebook/mbart-large-50-many-to-many-mmt (Many-to-many multilingual machine translation, 50 languages) facebook/mbart-large-50-many-to-one-mmt (Many-to-one multilingual machine translation, 50 languages) facebook/mbart-large-50 (Multilingual translation, 50 languages) facebook/mbart-large-cc25 In this example, load the facebook/mbart-large-50-many-to-many-mmt checkpoint to translate Finnish to English. You can set the source language in the tokenizer: from transformers import AutoTokenizer, AutoModelForSeq2SeqLM en_text = "Do not meddle in the affairs of wizards, for they are subtle and quick to anger." fi_text = "Älä sekaannu velhojen asioihin, sillä ne ovat hienovaraisia ja nopeasti vihaisia." tokenizer = AutoTokenizer.from_pretrained("facebook/mbart-large-50-many-to-many-mmt", src_lang="fi_FI") model = AutoModelForSeq2SeqLM.from_pretrained("facebook/mbart-large-50-many-to-many-mmt") Tokenize the text: encoded_en = tokenizer(en_text, return_tensors="pt") MBart forces the target language id as the first generated token to translate to the target language. Set the forced_bos_token_id to en in the generate method to translate to English: generated_tokens = model.generate(**encoded_en, forced_bos_token_id=tokenizer.lang_code_to_id("en_XX")) tokenizer.batch_decode(generated_tokens, skip_special_tokens=True) "Don't interfere with the wizard's affairs, because they are subtle, will soon get angry." If you are using the facebook/mbart-large-50-many-to-one-mmt checkpoint, you don't need to force the target language id as the first generated token otherwise the usage is the same.