mirror of https://github.com/explosion/spaCy.git
940 lines
34 KiB
Markdown
940 lines
34 KiB
Markdown
---
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title: Layers and Model Architectures
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teaser: Power spaCy components with custom neural networks
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menu:
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- ['Type Signatures', 'type-sigs']
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- ['Swapping Architectures', 'swap-architectures']
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- ['PyTorch & TensorFlow', 'frameworks']
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- ['Custom Thinc Models', 'thinc']
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- ['Trainable Components', 'components']
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next: /usage/projects
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---
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> #### Example
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>
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> ```python
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> from thinc.api import Model, chain
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>
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> @spacy.registry.architectures.register("model.v1")
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> def build_model(width: int, classes: int) -> Model:
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> tok2vec = build_tok2vec(width)
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> output_layer = build_output_layer(width, classes)
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> model = chain(tok2vec, output_layer)
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> return model
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> ```
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A **model architecture** is a function that wires up a
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[Thinc `Model`](https://thinc.ai/docs/api-model) instance. It describes the
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neural network that is run internally as part of a component in a spaCy
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pipeline. To define the actual architecture, you can implement your logic in
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Thinc directly, or you can use Thinc as a thin wrapper around frameworks such as
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PyTorch, TensorFlow and MXNet. Each `Model` can also be used as a sublayer of a
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larger network, allowing you to freely combine implementations from different
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frameworks into a single model.
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spaCy's built-in components require a `Model` instance to be passed to them via
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the config system. To change the model architecture of an existing component,
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you just need to [**update the config**](#swap-architectures) so that it refers
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to a different registered function. Once the component has been created from
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this config, you won't be able to change it anymore. The architecture is like a
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recipe for the network, and you can't change the recipe once the dish has
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already been prepared. You have to make a new one.
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```ini
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### config.cfg (excerpt)
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[components.tagger]
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factory = "tagger"
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[components.tagger.model]
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@architectures = "model.v1"
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width = 512
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classes = 16
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```
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## Type signatures {#type-sigs}
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> #### Example
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>
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> ```python
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> from typing import List
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> from thinc.api import Model, chain
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> from thinc.types import Floats2d
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> def chain_model(
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> tok2vec: Model[List[Doc], List[Floats2d]],
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> layer1: Model[List[Floats2d], Floats2d],
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> layer2: Model[Floats2d, Floats2d]
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> ) -> Model[List[Doc], Floats2d]:
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> model = chain(tok2vec, layer1, layer2)
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> return model
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> ```
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The Thinc `Model` class is a **generic type** that can specify its input and
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output types. Python uses a square-bracket notation for this, so the type
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~~Model[List, Dict]~~ says that each batch of inputs to the model will be a
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list, and the outputs will be a dictionary. You can be even more specific and
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write for instance~~Model[List[Doc], Dict[str, float]]~~ to specify that the
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model expects a list of [`Doc`](/api/doc) objects as input, and returns a
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dictionary mapping of strings to floats. Some of the most common types you'll
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see are:
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| Type | Description |
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| ------------------ | ---------------------------------------------------------------------------------------------------- |
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| ~~List[Doc]~~ | A batch of [`Doc`](/api/doc) objects. Most components expect their models to take this as input. |
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| ~~Floats2d~~ | A two-dimensional `numpy` or `cupy` array of floats. Usually 32-bit. |
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| ~~Ints2d~~ | A two-dimensional `numpy` or `cupy` array of integers. Common dtypes include uint64, int32 and int8. |
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| ~~List[Floats2d]~~ | A list of two-dimensional arrays, generally with one array per `Doc` and one row per token. |
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| ~~Ragged~~ | A container to handle variable-length sequence data in an unpadded contiguous array. |
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| ~~Padded~~ | A container to handle variable-length sequence data in a padded contiguous array. |
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See the [Thinc type reference](https://thinc.ai/docs/api-types) for details. The
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model type signatures help you figure out which model architectures and
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components can **fit together**. For instance, the
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[`TextCategorizer`](/api/textcategorizer) class expects a model typed
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~~Model[List[Doc], Floats2d]~~, because the model will predict one row of
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category probabilities per [`Doc`](/api/doc). In contrast, the
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[`Tagger`](/api/tagger) class expects a model typed ~~Model[List[Doc],
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List[Floats2d]]~~, because it needs to predict one row of probabilities per
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token.
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There's no guarantee that two models with the same type signature can be used
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interchangeably. There are many other ways they could be incompatible. However,
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if the types don't match, they almost surely _won't_ be compatible. This little
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bit of validation goes a long way, especially if you
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[configure your editor](https://thinc.ai/docs/usage-type-checking) or other
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tools to highlight these errors early. The config file is also validated at the
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beginning of training, to verify that all the types match correctly.
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<Accordion title="Tip: Static type checking in your editor">
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If you're using a modern editor like Visual Studio Code, you can
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[set up `mypy`](https://thinc.ai/docs/usage-type-checking#install) with the
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custom Thinc plugin and get live feedback about mismatched types as you write
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code.
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[![](../images/thinc_mypy.jpg)](https://thinc.ai/docs/usage-type-checking#linting)
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</Accordion>
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## Swapping model architectures {#swap-architectures}
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If no model is specified for the [`TextCategorizer`](/api/textcategorizer), the
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[TextCatEnsemble](/api/architectures#TextCatEnsemble) architecture is used by
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default. This architecture combines a simple bag-of-words model with a neural
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network, usually resulting in the most accurate results, but at the cost of
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speed. The config file for this model would look something like this:
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```ini
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### config.cfg (excerpt)
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[components.textcat]
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factory = "textcat"
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labels = []
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[components.textcat.model]
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@architectures = "spacy.TextCatEnsemble.v2"
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nO = null
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[components.textcat.model.tok2vec]
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@architectures = "spacy.Tok2Vec.v1"
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[components.textcat.model.tok2vec.embed]
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@architectures = "spacy.MultiHashEmbed.v1"
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width = 64
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rows = [2000, 2000, 1000, 1000, 1000, 1000]
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attrs = ["ORTH", "LOWER", "PREFIX", "SUFFIX", "SHAPE", "ID"]
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include_static_vectors = false
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[components.textcat.model.tok2vec.encode]
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@architectures = "spacy.MaxoutWindowEncoder.v1"
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width = ${components.textcat.model.tok2vec.embed.width}
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window_size = 1
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maxout_pieces = 3
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depth = 2
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[components.textcat.model.linear_model]
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@architectures = "spacy.TextCatBOW.v1"
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exclusive_classes = false
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ngram_size = 1
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no_output_layer = false
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```
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spaCy has two additional built-in `textcat` architectures, and you can easily
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use those by swapping out the definition of the textcat's model. For instance,
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to use the simple and fast bag-of-words model
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[TextCatBOW](/api/architectures#TextCatBOW), you can change the config to:
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```ini
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### config.cfg (excerpt) {highlight="6-10"}
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[components.textcat]
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factory = "textcat"
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labels = []
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[components.textcat.model]
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@architectures = "spacy.TextCatBOW.v1"
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exclusive_classes = false
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ngram_size = 1
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no_output_layer = false
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nO = null
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```
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For details on all pre-defined architectures shipped with spaCy and how to
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configure them, check out the [model architectures](/api/architectures)
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documentation.
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### Defining sublayers {#sublayers}
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Model architecture functions often accept **sublayers as arguments**, so that
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you can try **substituting a different layer** into the network. Depending on
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how the architecture function is structured, you might be able to define your
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network structure entirely through the [config system](/usage/training#config),
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using layers that have already been defined.
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In most neural network models for NLP, the most important parts of the network
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are what we refer to as the
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[embed and encode](https://explosion.ai/blog/deep-learning-formula-nlp) steps.
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These steps together compute dense, context-sensitive representations of the
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tokens, and their combination forms a typical
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[`Tok2Vec`](/api/architectures#Tok2Vec) layer:
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```ini
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### config.cfg (excerpt)
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[components.tok2vec]
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factory = "tok2vec"
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[components.tok2vec.model]
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@architectures = "spacy.Tok2Vec.v1"
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[components.tok2vec.model.embed]
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@architectures = "spacy.MultiHashEmbed.v1"
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# ...
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[components.tok2vec.model.encode]
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@architectures = "spacy.MaxoutWindowEncoder.v1"
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# ...
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```
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By defining these sublayers specifically, it becomes straightforward to swap out
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a sublayer for another one, for instance changing the first sublayer to a
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character embedding with the [CharacterEmbed](/api/architectures#CharacterEmbed)
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architecture:
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```ini
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### config.cfg (excerpt)
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[components.tok2vec.model.embed]
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@architectures = "spacy.CharacterEmbed.v1"
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# ...
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[components.tok2vec.model.encode]
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@architectures = "spacy.MaxoutWindowEncoder.v1"
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# ...
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```
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Most of spaCy's default architectures accept a `tok2vec` layer as a sublayer
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within the larger task-specific neural network. This makes it easy to **switch
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between** transformer, CNN, BiLSTM or other feature extraction approaches. The
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[transformers documentation](/usage/embeddings-transformers#training-custom-model)
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section shows an example of swapping out a model's standard `tok2vec` layer with
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a transformer. And if you want to define your own solution, all you need to do
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is register a ~~Model[List[Doc], List[Floats2d]]~~ architecture function, and
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you'll be able to try it out in any of the spaCy components.
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## Wrapping PyTorch, TensorFlow and other frameworks {#frameworks}
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Thinc allows you to [wrap models](https://thinc.ai/docs/usage-frameworks)
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written in other machine learning frameworks like PyTorch, TensorFlow and MXNet
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using a unified [`Model`](https://thinc.ai/docs/api-model) API. This makes it
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easy to use a model implemented in a different framework to power a component in
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your spaCy pipeline. For example, to wrap a PyTorch model as a Thinc `Model`,
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you can use Thinc's
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[`PyTorchWrapper`](https://thinc.ai/docs/api-layers#pytorchwrapper):
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```python
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from thinc.api import PyTorchWrapper
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wrapped_pt_model = PyTorchWrapper(torch_model)
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```
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Let's use PyTorch to define a very simple neural network consisting of two
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hidden `Linear` layers with `ReLU` activation and dropout, and a
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softmax-activated output layer:
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```python
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### PyTorch model
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from torch import nn
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torch_model = nn.Sequential(
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nn.Linear(width, hidden_width),
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nn.ReLU(),
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nn.Dropout2d(dropout),
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nn.Linear(hidden_width, nO),
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nn.ReLU(),
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nn.Dropout2d(dropout),
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nn.Softmax(dim=1)
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)
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```
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The resulting wrapped `Model` can be used as a **custom architecture** as such,
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or can be a **subcomponent of a larger model**. For instance, we can use Thinc's
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[`chain`](https://thinc.ai/docs/api-layers#chain) combinator, which works like
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`Sequential` in PyTorch, to combine the wrapped model with other components in a
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larger network. This effectively means that you can easily wrap different
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components from different frameworks, and "glue" them together with Thinc:
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```python
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from thinc.api import chain, with_array, PyTorchWrapper
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from spacy.ml import CharacterEmbed
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wrapped_pt_model = PyTorchWrapper(torch_model)
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char_embed = CharacterEmbed(width, embed_size, nM, nC)
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model = chain(char_embed, with_array(wrapped_pt_model))
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```
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In the above example, we have combined our custom PyTorch model with a character
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embedding layer defined by spaCy.
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[CharacterEmbed](/api/architectures#CharacterEmbed) returns a `Model` that takes
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a ~~List[Doc]~~ as input, and outputs a ~~List[Floats2d]~~. To make sure that
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the wrapped PyTorch model receives valid inputs, we use Thinc's
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[`with_array`](https://thinc.ai/docs/api-layers#with_array) helper.
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You could also implement a model that only uses PyTorch for the transformer
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layers, and "native" Thinc layers to do fiddly input and output transformations
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and add on task-specific "heads", as efficiency is less of a consideration for
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those parts of the network.
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### Using wrapped models {#frameworks-usage}
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To use our custom model including the PyTorch subnetwork, all we need to do is
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register the architecture using the
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[`architectures` registry](/api/top-level#registry). This assigns the
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architecture a name so spaCy knows how to find it, and allows passing in
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arguments like hyperparameters via the [config](/usage/training#config). The
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full example then becomes:
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```python
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### Registering the architecture {highlight="9"}
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from typing import List
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from thinc.types import Floats2d
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from thinc.api import Model, PyTorchWrapper, chain, with_array
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import spacy
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from spacy.tokens.doc import Doc
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from spacy.ml import CharacterEmbed
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from torch import nn
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@spacy.registry.architectures("CustomTorchModel.v1")
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def create_torch_model(
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nO: int,
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width: int,
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hidden_width: int,
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embed_size: int,
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nM: int,
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nC: int,
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dropout: float,
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) -> Model[List[Doc], List[Floats2d]]:
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char_embed = CharacterEmbed(width, embed_size, nM, nC)
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torch_model = nn.Sequential(
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nn.Linear(width, hidden_width),
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nn.ReLU(),
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nn.Dropout2d(dropout),
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nn.Linear(hidden_width, nO),
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nn.ReLU(),
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nn.Dropout2d(dropout),
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nn.Softmax(dim=1)
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)
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wrapped_pt_model = PyTorchWrapper(torch_model)
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model = chain(char_embed, with_array(wrapped_pt_model))
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return model
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```
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The model definition can now be used in any existing trainable spaCy component,
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by specifying it in the config file. In this configuration, all required
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parameters for the various subcomponents of the custom architecture are passed
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in as settings via the config.
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```ini
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### config.cfg (excerpt) {highlight="5-5"}
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[components.tagger]
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factory = "tagger"
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[components.tagger.model]
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@architectures = "CustomTorchModel.v1"
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nO = 50
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width = 96
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hidden_width = 48
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embed_size = 2000
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nM = 64
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nC = 8
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dropout = 0.2
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```
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<Infobox variant="warning">
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Remember that it is best not to rely on any (hidden) default values to ensure
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that training configs are complete and experiments fully reproducible.
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</Infobox>
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Note that when using a PyTorch or Tensorflow model, it is recommended to set the
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GPU memory allocator accordingly. When `gpu_allocator` is set to "pytorch" or
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"tensorflow" in the training config, cupy will allocate memory via those
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respective libraries, preventing OOM errors when there's available memory
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sitting in the other library's pool.
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```ini
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### config.cfg (excerpt)
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[training]
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gpu_allocator = "pytorch"
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```
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## Custom models with Thinc {#thinc}
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Of course it's also possible to define the `Model` from the previous section
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entirely in Thinc. The Thinc documentation provides details on the
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[various layers](https://thinc.ai/docs/api-layers) and helper functions
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available. Combinators can be used to
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[overload operators](https://thinc.ai/docs/usage-models#operators) and a common
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usage pattern is to bind `chain` to `>>`. The "native" Thinc version of our
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simple neural network would then become:
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```python
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from thinc.api import chain, with_array, Model, Relu, Dropout, Softmax
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from spacy.ml import CharacterEmbed
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char_embed = CharacterEmbed(width, embed_size, nM, nC)
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with Model.define_operators({">>": chain}):
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layers = (
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Relu(hidden_width, width)
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>> Dropout(dropout)
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>> Relu(hidden_width, hidden_width)
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>> Dropout(dropout)
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>> Softmax(nO, hidden_width)
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)
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model = char_embed >> with_array(layers)
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```
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<Infobox variant="warning" title="Important note on inputs and outputs">
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Note that Thinc layers define the output dimension (`nO`) as the first argument,
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followed (optionally) by the input dimension (`nI`). This is in contrast to how
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the PyTorch layers are defined, where `in_features` precedes `out_features`.
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</Infobox>
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### Shape inference in Thinc {#thinc-shape-inference}
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It is **not** strictly necessary to define all the input and output dimensions
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for each layer, as Thinc can perform
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[shape inference](https://thinc.ai/docs/usage-models#validation) between
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sequential layers by matching up the output dimensionality of one layer to the
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input dimensionality of the next. This means that we can simplify the `layers`
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definition:
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> #### Diff
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>
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> ```diff
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> layers = (
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> Relu(hidden_width, width)
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> >> Dropout(dropout)
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> - >> Relu(hidden_width, hidden_width)
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> + >> Relu(hidden_width)
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> >> Dropout(dropout)
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> - >> Softmax(nO, hidden_width)
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> + >> Softmax(nO)
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> )
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> ```
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```python
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with Model.define_operators({">>": chain}):
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layers = (
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Relu(hidden_width, width)
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>> Dropout(dropout)
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>> Relu(hidden_width)
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>> Dropout(dropout)
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>> Softmax(nO)
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)
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```
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Thinc can even go one step further and **deduce the correct input dimension** of
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the first layer, and output dimension of the last. To enable this functionality,
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you have to call
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[`Model.initialize`](https://thinc.ai/docs/api-model#initialize) with an **input
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sample** `X` and an **output sample** `Y` with the correct dimensions:
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```python
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### Shape inference with initialization {highlight="3,7,10"}
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with Model.define_operators({">>": chain}):
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layers = (
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Relu(hidden_width)
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>> Dropout(dropout)
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>> Relu(hidden_width)
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>> Dropout(dropout)
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>> Softmax()
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)
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model = char_embed >> with_array(layers)
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model.initialize(X=input_sample, Y=output_sample)
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```
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||
|
||
The built-in [pipeline components](/usage/processing-pipelines) in spaCy ensure
|
||
that their internal models are **always initialized** with appropriate sample
|
||
data. In this case, `X` is typically a ~~List[Doc]~~, while `Y` is typically a
|
||
~~List[Array1d]~~ or ~~List[Array2d]~~, depending on the specific task. This
|
||
functionality is triggered when [`nlp.initialize`](/api/language#initialize) is
|
||
called.
|
||
|
||
### Dropout and normalization in Thinc {#thinc-dropout-norm}
|
||
|
||
Many of the available Thinc [layers](https://thinc.ai/docs/api-layers) allow you
|
||
to define a `dropout` argument that will result in "chaining" an additional
|
||
[`Dropout`](https://thinc.ai/docs/api-layers#dropout) layer. Optionally, you can
|
||
often specify whether or not you want to add layer normalization, which would
|
||
result in an additional
|
||
[`LayerNorm`](https://thinc.ai/docs/api-layers#layernorm) layer. That means that
|
||
the following `layers` definition is equivalent to the previous:
|
||
|
||
```python
|
||
with Model.define_operators({">>": chain}):
|
||
layers = (
|
||
Relu(hidden_width, dropout=dropout, normalize=False)
|
||
>> Relu(hidden_width, dropout=dropout, normalize=False)
|
||
>> Softmax()
|
||
)
|
||
model = char_embed >> with_array(layers)
|
||
model.initialize(X=input_sample, Y=output_sample)
|
||
```
|
||
|
||
## Create new trainable components {#components}
|
||
|
||
In addition to [swapping out](#swap-architectures) default models in built-in
|
||
components, you can also implement an entirely new,
|
||
[trainable](/usage/processing-pipelines#trainable-components) pipeline component
|
||
from scratch. This can be done by creating a new class inheriting from
|
||
[`TrainablePipe`](/api/pipe), and linking it up to your custom model
|
||
implementation.
|
||
|
||
<Infobox title="Trainable component API" emoji="💡">
|
||
|
||
For details on how to implement pipeline components, check out the usage guide
|
||
on [custom components](/usage/processing-pipelines#custom-component) and the
|
||
overview of the `TrainablePipe` methods used by
|
||
[trainable components](/usage/processing-pipelines#trainable-components).
|
||
|
||
</Infobox>
|
||
|
||
### Example: Entity relation extraction component {#component-rel}
|
||
|
||
This section outlines an example use-case of implementing a **novel relation
|
||
extraction component** from scratch. We'll implement a binary relation
|
||
extraction method that determines whether or not **two entities** in a document
|
||
are related, and if so, what type of relation. We'll allow multiple types of
|
||
relations between two such entities (multi-label setting). There are two major
|
||
steps required:
|
||
|
||
1. Implement a [machine learning model](#component-rel-model) specific to this
|
||
task. It will have to extract candidates from a [`Doc`](/api/doc) and predict
|
||
a relation for the available candidate pairs.
|
||
2. Implement a custom [pipeline component](#component-rel-pipe) powered by the
|
||
machine learning model that sets annotations on the [`Doc`](/api/doc) passing
|
||
through the pipeline.
|
||
|
||
<Project id="tutorials/rel_component">
|
||
Run this example use-case by using our project template. It includes all the
|
||
code to create the ML model and the pipeline component from scratch.
|
||
It contains two config files to train the model:
|
||
one to run on CPU with a Tok2Vec layer, and one for the GPU using a transformer.
|
||
The project applies the relation extraction component to identify biomolecular
|
||
interactions, but you can easily swap in your own dataset for your experiments.
|
||
</Project>
|
||
|
||
#### Step 1: Implementing the Model {#component-rel-model}
|
||
|
||
We need to implement a [`Model`](https://thinc.ai/docs/api-model) that takes a
|
||
**list of documents** (~~List[Doc]~~) as input, and outputs a **two-dimensional
|
||
matrix** (~~Floats2d~~) of predictions:
|
||
|
||
> #### Model type annotations
|
||
>
|
||
> The `Model` class is a generic type that can specify its input and output
|
||
> types, e.g. ~~Model[List[Doc], Floats2d]~~. Type hints are used for static
|
||
> type checks and validation. See the section on [type signatures](#type-sigs)
|
||
> for details.
|
||
|
||
```python
|
||
### Register the model architecture
|
||
@registry.architectures.register("rel_model.v1")
|
||
def create_relation_model(...) -> Model[List[Doc], Floats2d]:
|
||
model = ... # 👈 model will go here
|
||
return model
|
||
```
|
||
|
||
The first layer in this model will typically be an
|
||
[embedding layer](/usage/embeddings-transformers) such as a
|
||
[`Tok2Vec`](/api/tok2vec) component or a [`Transformer`](/api/transformer). This
|
||
layer is assumed to be of type ~~Model[List[Doc], List[Floats2d]]~~ as it
|
||
transforms each **document into a list of tokens**, with each token being
|
||
represented by its embedding in the vector space.
|
||
|
||
Next, we need a method that **generates pairs of entities** that we want to
|
||
classify as being related or not. As these candidate pairs are typically formed
|
||
within one document, this function takes a [`Doc`](/api/doc) as input and
|
||
outputs a `List` of `Span` tuples. For instance, a very straightforward
|
||
implementation would be to just take any two entities from the same document:
|
||
|
||
```python
|
||
### Simple candiate generation
|
||
def get_candidates(doc: Doc) -> List[Tuple[Span, Span]]:
|
||
candidates = []
|
||
for ent1 in doc.ents:
|
||
for ent2 in doc.ents:
|
||
candidates.append((ent1, ent2))
|
||
return candidates
|
||
```
|
||
|
||
But we could also refine this further by **excluding relations** of an entity
|
||
with itself, and posing a **maximum distance** (in number of tokens) between two
|
||
entities. We register this function in the
|
||
[`@misc` registry](/api/top-level#registry) so we can refer to it from the
|
||
config, and easily swap it out for any other candidate generation function.
|
||
|
||
> #### config.cfg (excerpt)
|
||
>
|
||
> ```ini
|
||
> [model]
|
||
> @architectures = "rel_model.v1"
|
||
>
|
||
> [model.tok2vec]
|
||
> # ...
|
||
>
|
||
> [model.get_candidates]
|
||
> @misc = "rel_cand_generator.v1"
|
||
> max_length = 20
|
||
> ```
|
||
|
||
```python
|
||
### Extended candidate generation {highlight="1,2,7,8"}
|
||
@registry.misc.register("rel_cand_generator.v1")
|
||
def create_candidate_indices(max_length: int) -> Callable[[Doc], List[Tuple[Span, Span]]]:
|
||
def get_candidates(doc: "Doc") -> List[Tuple[Span, Span]]:
|
||
candidates = []
|
||
for ent1 in doc.ents:
|
||
for ent2 in doc.ents:
|
||
if ent1 != ent2:
|
||
if max_length and abs(ent2.start - ent1.start) <= max_length:
|
||
candidates.append((ent1, ent2))
|
||
return candidates
|
||
return get_candidates
|
||
```
|
||
|
||
Finally, we require a method that transforms the candidate entity pairs into a
|
||
2D tensor using the specified [`Tok2Vec`](/api/tok2vec) or
|
||
[`Transformer`](/api/transformer). The resulting ~~Floats2~~ object will then be
|
||
processed by a final `output_layer` of the network. Putting all this together,
|
||
we can define our relation model in a config file as such:
|
||
|
||
```ini
|
||
### config.cfg
|
||
[model]
|
||
@architectures = "rel_model.v1"
|
||
# ...
|
||
|
||
[model.tok2vec]
|
||
# ...
|
||
|
||
[model.get_candidates]
|
||
@misc = "rel_cand_generator.v1"
|
||
max_length = 20
|
||
|
||
[model.create_candidate_tensor]
|
||
@misc = "rel_cand_tensor.v1"
|
||
|
||
[model.output_layer]
|
||
@architectures = "rel_output_layer.v1"
|
||
# ...
|
||
```
|
||
|
||
<!-- TODO: link to project for implementation details -->
|
||
<!-- TODO: maybe embed files from project that show the architectures? -->
|
||
|
||
When creating this model, we store the custom functions as
|
||
[attributes](https://thinc.ai/docs/api-model#properties) and the sublayers as
|
||
references, so we can access them easily:
|
||
|
||
```python
|
||
tok2vec_layer = model.get_ref("tok2vec")
|
||
output_layer = model.get_ref("output_layer")
|
||
create_candidate_tensor = model.attrs["create_candidate_tensor"]
|
||
get_candidates = model.attrs["get_candidates"]
|
||
```
|
||
|
||
#### Step 2: Implementing the pipeline component {#component-rel-pipe}
|
||
|
||
To use our new relation extraction model as part of a custom
|
||
[trainable component](/usage/processing-pipelines#trainable-components), we
|
||
create a subclass of [`TrainablePipe`](/api/pipe) that holds the model.
|
||
|
||
![Illustration of Pipe methods](../images/trainable_component.svg)
|
||
|
||
```python
|
||
### Pipeline component skeleton
|
||
from spacy.pipeline import TrainablePipe
|
||
|
||
class RelationExtractor(TrainablePipe):
|
||
def __init__(self, vocab, model, name="rel"):
|
||
"""Create a component instance."""
|
||
self.model = model
|
||
self.vocab = vocab
|
||
self.name = name
|
||
|
||
def update(self, examples, drop=0.0, set_annotations=False, sgd=None, losses=None):
|
||
"""Learn from a batch of Example objects."""
|
||
...
|
||
|
||
def predict(self, docs):
|
||
"""Apply the model to a batch of Doc objects."""
|
||
...
|
||
|
||
def set_annotations(self, docs, predictions):
|
||
"""Modify a batch of Doc objects using the predictions."""
|
||
...
|
||
|
||
def initialize(self, get_examples, nlp=None, labels=None):
|
||
"""Initialize the model before training."""
|
||
...
|
||
|
||
def add_label(self, label):
|
||
"""Add a label to the component."""
|
||
...
|
||
```
|
||
|
||
Before the model can be used, it needs to be
|
||
[initialized](/usage/training#initialization). This function receives a callback
|
||
to access the full **training data set**, or a representative sample. This data
|
||
set can be used to deduce all **relevant labels**. Alternatively, a list of
|
||
labels can be provided to `initialize`, or you can call
|
||
`RelationExtractor.add_label` directly. The number of labels defines the output
|
||
dimensionality of the network, and will be used to do
|
||
[shape inference](https://thinc.ai/docs/usage-models#validation) throughout the
|
||
layers of the neural network. This is triggered by calling
|
||
[`Model.initialize`](https://thinc.ai/api/model#initialize).
|
||
|
||
```python
|
||
### The initialize method {highlight="12,18,22"}
|
||
from itertools import islice
|
||
|
||
def initialize(
|
||
self,
|
||
get_examples: Callable[[], Iterable[Example]],
|
||
*,
|
||
nlp: Language = None,
|
||
labels: Optional[List[str]] = None,
|
||
):
|
||
if labels is not None:
|
||
for label in labels:
|
||
self.add_label(label)
|
||
else:
|
||
for example in get_examples():
|
||
relations = example.reference._.rel
|
||
for indices, label_dict in relations.items():
|
||
for label in label_dict.keys():
|
||
self.add_label(label)
|
||
subbatch = list(islice(get_examples(), 10))
|
||
doc_sample = [eg.reference for eg in subbatch]
|
||
label_sample = self._examples_to_truth(subbatch)
|
||
self.model.initialize(X=doc_sample, Y=label_sample)
|
||
```
|
||
|
||
The `initialize` method is triggered whenever this component is part of an `nlp`
|
||
pipeline, and [`nlp.initialize`](/api/language#initialize) is invoked.
|
||
Typically, this happens when the pipeline is set up before training in
|
||
[`spacy train`](/api/cli#training). After initialization, the pipeline component
|
||
and its internal model can be trained and used to make predictions.
|
||
|
||
During training, the function [`update`](/api/pipe#update) is invoked which
|
||
delegates to
|
||
[`Model.begin_update`](https://thinc.ai/docs/api-model#begin_update) and a
|
||
[`get_loss`](/api/pipe#get_loss) function that **calculates the loss** for a
|
||
batch of examples, as well as the **gradient** of loss that will be used to
|
||
update the weights of the model layers. Thinc provides several
|
||
[loss functions](https://thinc.ai/docs/api-loss) that can be used for the
|
||
implementation of the `get_loss` function.
|
||
|
||
```python
|
||
### The update method {highlight="12-14"}
|
||
def update(
|
||
self,
|
||
examples: Iterable[Example],
|
||
*,
|
||
drop: float = 0.0,
|
||
set_annotations: bool = False,
|
||
sgd: Optional[Optimizer] = None,
|
||
losses: Optional[Dict[str, float]] = None,
|
||
) -> Dict[str, float]:
|
||
...
|
||
docs = [ex.predicted for ex in examples]
|
||
predictions, backprop = self.model.begin_update(docs)
|
||
loss, gradient = self.get_loss(examples, predictions)
|
||
backprop(gradient)
|
||
losses[self.name] += loss
|
||
...
|
||
return losses
|
||
```
|
||
|
||
When the internal model is trained, the component can be used to make novel
|
||
**predictions**. The [`predict`](/api/pipe#predict) function needs to be
|
||
implemented for each subclass of `TrainablePipe`. In our case, we can simply
|
||
delegate to the internal model's
|
||
[predict](https://thinc.ai/docs/api-model#predict) function that takes a batch
|
||
of `Doc` objects and returns a ~~Floats2d~~ array:
|
||
|
||
```python
|
||
### The predict method
|
||
def predict(self, docs: Iterable[Doc]) -> Floats2d:
|
||
predictions = self.model.predict(docs)
|
||
return self.model.ops.asarray(predictions)
|
||
```
|
||
|
||
The final method that needs to be implemented, is
|
||
[`set_annotations`](/api/pipe#set_annotations). This function takes the
|
||
predictions, and modifies the given `Doc` object in place to store them. For our
|
||
relation extraction component, we store the data as a dictionary in a custom
|
||
[extension attribute](/usage/processing-pipelines#custom-components-attributes)
|
||
`doc._.rel`. As keys, we represent the candidate pair by the **start offsets of
|
||
each entity**, as this defines an entity pair uniquely within one document.
|
||
|
||
To interpret the scores predicted by the relation extraction model correctly, we
|
||
need to refer to the model's `get_candidates` function that defined which pairs
|
||
of entities were relevant candidates, so that the predictions can be linked to
|
||
those exact entities:
|
||
|
||
> #### Example output
|
||
>
|
||
> ```python
|
||
> doc = nlp("Amsterdam is the capital of the Netherlands.")
|
||
> print("spans", [(e.start, e.text, e.label_) for e in doc.ents])
|
||
> for value, rel_dict in doc._.rel.items():
|
||
> print(f"{value}: {rel_dict}")
|
||
>
|
||
> # spans [(0, 'Amsterdam', 'LOC'), (6, 'Netherlands', 'LOC')]
|
||
> # (0, 6): {'CAPITAL_OF': 0.89, 'LOCATED_IN': 0.75, 'UNRELATED': 0.002}
|
||
> # (6, 0): {'CAPITAL_OF': 0.01, 'LOCATED_IN': 0.13, 'UNRELATED': 0.017}
|
||
> ```
|
||
|
||
```python
|
||
### Registering the extension attribute
|
||
from spacy.tokens import Doc
|
||
Doc.set_extension("rel", default={})
|
||
```
|
||
|
||
```python
|
||
### The set_annotations method {highlight="5-6,10"}
|
||
def set_annotations(self, docs: Iterable[Doc], predictions: Floats2d):
|
||
c = 0
|
||
get_candidates = self.model.attrs["get_candidates"]
|
||
for doc in docs:
|
||
for (e1, e2) in get_candidates(doc):
|
||
offset = (e1.start, e2.start)
|
||
if offset not in doc._.rel:
|
||
doc._.rel[offset] = {}
|
||
for j, label in enumerate(self.labels):
|
||
doc._.rel[offset][label] = predictions[c, j]
|
||
c += 1
|
||
```
|
||
|
||
Under the hood, when the pipe is applied to a document, it delegates to the
|
||
`predict` and `set_annotations` methods:
|
||
|
||
```python
|
||
### The __call__ method
|
||
def __call__(self, Doc doc):
|
||
predictions = self.predict([doc])
|
||
self.set_annotations([doc], predictions)
|
||
return doc
|
||
```
|
||
|
||
There is one more optional method to implement: [`score`](/api/pipe#score)
|
||
calculates the performance of your component on a set of examples, and
|
||
returns the results as a dictionary:
|
||
|
||
```python
|
||
### The score method
|
||
def score(self, examples: Iterable[Example]) -> Dict[str, Any]:
|
||
prf = PRFScore()
|
||
for example in examples:
|
||
...
|
||
|
||
return {
|
||
"rel_micro_p": prf.precision,
|
||
"rel_micro_r": prf.recall,
|
||
"rel_micro_f": prf.fscore,
|
||
}
|
||
```
|
||
|
||
This is particularly useful to see the scores on the development corpus
|
||
when training the component with [`spacy train`](/api/cli#training).
|
||
|
||
Once our `TrainablePipe` subclass is fully implemented, we can
|
||
[register](/usage/processing-pipelines#custom-components-factories) the
|
||
component with the [`@Language.factory`](/api/language#factory) decorator. This
|
||
assigns it a name and lets you create the component with
|
||
[`nlp.add_pipe`](/api/language#add_pipe) and via the
|
||
[config](/usage/training#config).
|
||
|
||
> #### config.cfg (excerpt)
|
||
>
|
||
> ```ini
|
||
> [components.relation_extractor]
|
||
> factory = "relation_extractor"
|
||
>
|
||
> [components.relation_extractor.model]
|
||
> @architectures = "rel_model.v1"
|
||
>
|
||
> [components.relation_extractor.model.tok2vec]
|
||
> # ...
|
||
>
|
||
> [components.relation_extractor.model.get_candidates]
|
||
> @misc = "rel_cand_generator.v1"
|
||
> max_length = 20
|
||
>
|
||
> [training.score_weights]
|
||
> rel_micro_p = 0.0
|
||
> rel_micro_r = 0.0
|
||
> rel_micro_f = 1.0
|
||
> ```
|
||
|
||
```python
|
||
### Registering the pipeline component
|
||
from spacy.language import Language
|
||
|
||
@Language.factory("relation_extractor")
|
||
def make_relation_extractor(nlp, name, model):
|
||
return RelationExtractor(nlp.vocab, model, name)
|
||
```
|
||
|
||
You can extend the decorator to include information such as the type of
|
||
annotations that are required for this component to run, the type of annotations
|
||
it produces, and the scores that can be calculated:
|
||
|
||
```python
|
||
### Factory annotations {highlight="5-11"}
|
||
from spacy.language import Language
|
||
|
||
@Language.factory(
|
||
"relation_extractor",
|
||
requires=["doc.ents", "token.ent_iob", "token.ent_type"],
|
||
assigns=["doc._.rel"],
|
||
default_score_weights={
|
||
"rel_micro_p": None,
|
||
"rel_micro_r": None,
|
||
"rel_micro_f": None,
|
||
},
|
||
)
|
||
def make_relation_extractor(nlp, name, model):
|
||
return RelationExtractor(nlp.vocab, model, name)
|
||
```
|
||
|
||
<Project id="tutorials/rel_component">
|
||
Run this example use-case by using our project template. It includes all the
|
||
code to create the ML model and the pipeline component from scratch.
|
||
It contains two config files to train the model:
|
||
one to run on CPU with a Tok2Vec layer, and one for the GPU using a transformer.
|
||
The project applies the relation extraction component to identify biomolecular
|
||
interactions, but you can easily swap in your own dataset for your experiments.
|
||
</Project>
|