52 lines
2.1 KiB
Markdown
52 lines
2.1 KiB
Markdown
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---
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title: Custom Layers
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short_title: Custom Layers
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description: Extend DL4J functionality for custom layers.
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category: Models
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weight: 10
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---
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## Writing Your Custom Layer
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There are two components to adding a custom layer:
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1. Adding the layer configuration class: extends org.deeplearning4j.nn.conf.layers.Layer
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2. Adding the layer implementation class: implements org.deeplearning4j.nn.api.Layer
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The configuration layer ((1) above) class handles the settings. It's the one you would
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use when constructing a MultiLayerNetwork or ComputationGraph. You can add custom
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settings here, and use them in your layer.
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The implementation layer ((2) above) class has parameters, and handles network forward
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pass, backpropagation, etc. It is created from the org.deeplearning4j.nn.conf.layers.Layer.instantiate(...)
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method. In other words: the instantiate method is how we go from the configuration
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to the implementation; MultiLayerNetwork or ComputationGraph will call this method
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when initializing the
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An example of these are CustomLayer (the configuration class) and CustomLayerImpl (the
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implementation class). Both of these classes have extensive comments regarding
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their methods.
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You'll note that in Deeplearning4j there are two DenseLayer clases, two GravesLSTM classes,
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etc: the reason is because one is for the configuration, one is for the implementation.
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We have not followed this "same name" pattern here to hopefully avoid confusion.
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## Testing Your Custom Layer
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Once you have added a custom layer, it is necessary to run some tests to ensure
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it is correct.
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These tests should at a minimum include the following:
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1. Tests to ensure that the JSON configuration (to/from JSON) works correctly
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This is necessary for networks with your custom layer to function with both
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model serialization (saving) and Spark training.
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2. Gradient checks to ensure that the implementation is correct.
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## Example
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A full custom layer example is available in our [examples repository](https://github.com/deeplearning4j/dl4j-examples/tree/master/dl4j-examples/src/main/java/org/deeplearning4j/examples/misc/customlayers).
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## API
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{{autogenerated}}
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