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Matthew Honnibal 2020-08-22 17:11:28 +02:00
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website/docs/usage/embeddings-transformers.md
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@ -70,13 +70,14 @@ of performance.
## Shared embedding layers {#embedding-layers}
spaCy lets you share a single embedding layer and reuse it across multiple
components. This is also known as **multi-task learning**. Sharing weights
between components can make your pipeline run a lot faster and result in a much
smaller models size, as you only need a single copy of the embeddings. However,
it can make the pipeline less modular and make it more difficult to swap
components or retrain parts of the pipeline, since all components depend on the
same weights.
spaCy lets you share a single transformer or other token-to-vector ("tok2vec")
embedding layer between multiple components. You can even update the shared layer,
performing **multi-task learning**. Reusing the tok2vec layer between components
can make your pipeline run a lot faster and result in much
smaller models. However, it can make the pipeline less modular and make it more
difficult to swap components or retrain parts of the pipeline. Multi-task
learning can affect your accuracy (either positively or negatively), and may
require some retuning of your hyper-parameters.
![Pipeline components using a shared embedding component vs. independent embedding layers](../images/tok2vec.svg)
@ -86,10 +87,11 @@ same weights.
| ✅ **faster:** embed the documents once for your whole pipeline | ❌ **slower:** rerun the embedding for each component |
| ❌ **less composable:** all components require the same embedding component in the pipeline | ✅ **modular:** components can be moved and swapped freely |
a single token-to-vector embedding model between multiple components using the
[`Tok2Vec`](/api/tok2vec) component. Other components in your pipeline can
"connect" this component by including a **listener layer** like
[Tok2VecListener](/api/architectures#Tok2VecListener) within their model.
You can share a single transformer or other tok2vec model between multiple components
by adding a [`Transformer`](/api/transformer) or [`Tok2Vec`](/api/tok2vec) component
near the start of your pipeline. Components later in the pipeline can "connect"
to it by including a **listener layer** like [Tok2VecListener](/api/architectures#Tok2VecListener)
within their model.
![Pipeline components listening to shared embedding component](../images/tok2vec-listener.svg)
@ -100,8 +102,9 @@ listeners, allowing the listeners to **reuse the predictions** when they are
eventually called. A similar mechanism is used to pass gradients from the
listeners back to the model. The [`Transformer`](/api/transformer) component and
[TransformerListener](/api/architectures#TransformerListener) layer do the same
thing for transformer models, making it easy to share a single transformer model
across your whole pipeline.
thing for transformer models, but the `Transformer` component will also save the
transformer outputs to the `doc._.trf_data` extension attribute, giving you
access to them after the pipeline has finished running.
<!-- TODO: show example of implementation via config, side by side -->