ai.djl.nn.recurrent.RecurrentBlock Maven / Gradle / Ivy
/*
* Copyright 2019 Amazon.com, Inc. or its affiliates. All Rights Reserved.
*
* Licensed under the Apache License, Version 2.0 (the "License"). You may not use this file except in compliance
* with the License. A copy of the License is located at
*
* http://aws.amazon.com/apache2.0/
*
* or in the "license" file accompanying this file. This file is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES
* OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions
* and limitations under the License.
*/
package ai.djl.nn.recurrent;
import ai.djl.MalformedModelException;
import ai.djl.ndarray.types.LayoutType;
import ai.djl.ndarray.types.Shape;
import ai.djl.nn.AbstractBlock;
import ai.djl.nn.Block;
import ai.djl.nn.Parameter;
import ai.djl.nn.ParameterList;
import ai.djl.util.Pair;
import java.io.DataInputStream;
import java.io.IOException;
/**
* {@code RecurrentBlock} is an abstract implementation of recurrent neural networks.
*
* Recurrent neural networks are neural networks with hidden states. They are very popular for
* natural language processing tasks, and other tasks which involve sequential data.
*
*
This [article](http://karpathy.github.io/2015/05/21/rnn-effectiveness/) written by Andrej
* Karpathy provides a detailed explanation of recurrent neural networks.
*
*
Currently, vanilla RNN, LSTM and GRU are implemented, with both multi-layer and bidirectional
* support.
*/
public abstract class RecurrentBlock extends AbstractBlock {
private static final byte VERSION = 2;
private static final LayoutType[] EXPECTED_LAYOUT = {
LayoutType.BATCH, LayoutType.TIME, LayoutType.CHANNEL
};
protected long stateSize;
protected float dropRate;
protected int numLayers;
protected int gates;
protected boolean batchFirst;
protected boolean hasBiases;
protected boolean bidirectional;
protected boolean returnState;
/**
* Creates a {@code RecurrentBlock} object.
*
* @param builder the {@code Builder} that has the necessary configurations
*/
@SuppressWarnings("this-escape")
public RecurrentBlock(BaseBuilder builder) {
super(VERSION);
stateSize = builder.stateSize;
dropRate = builder.dropRate;
numLayers = builder.numLayers;
batchFirst = builder.batchFirst;
hasBiases = builder.hasBiases;
bidirectional = builder.bidirectional;
returnState = builder.returnState;
Parameter.Type[] parameterTypes =
hasBiases
? new Parameter.Type[] {Parameter.Type.WEIGHT, Parameter.Type.BIAS}
: new Parameter.Type[] {Parameter.Type.WEIGHT};
String[] directions = {"l"};
if (builder.bidirectional) {
directions = new String[] {"l", "r"};
}
String[] gateStrings = {"i2h", "h2h"};
for (int i = 0; i < numLayers; i++) {
for (Parameter.Type parameterType : parameterTypes) {
for (String direction : directions) {
for (String gateString : gateStrings) {
String name =
direction + '_' + i + '_' + gateString + '_' + parameterType.name();
addParameter(
Parameter.builder().setName(name).setType(parameterType).build());
}
}
}
}
}
/** {@inheritDoc} */
@Override
public Shape[] getOutputShapes(Shape[] inputs) {
Shape inputShape = inputs[0];
Shape outputShape =
new Shape(inputShape.get(0), inputShape.get(1), stateSize * getNumDirections());
if (!returnState) {
return new Shape[] {
outputShape,
};
}
return new Shape[] {
outputShape,
new Shape(
(long) numLayers * getNumDirections(),
inputShape.get((batchFirst) ? 0 : 1),
stateSize)
};
}
/** {@inheritDoc} */
@Override
protected void beforeInitialize(Shape... inputShapes) {
super.beforeInitialize(inputShapes);
Block.validateLayout(EXPECTED_LAYOUT, inputShapes[0].getLayout());
}
/** {@inheritDoc} */
@Override
public void prepare(Shape[] inputs) {
Shape inputShape = inputs[0];
ParameterList parameters = getDirectParameters();
for (Pair pair : parameters) {
String name = pair.getKey();
Parameter parameter = pair.getValue();
int layer = Integer.parseInt(name.split("_")[1]);
long inputSize = inputShape.get(2);
if (layer > 0) {
inputSize = stateSize * getNumDirections();
}
if (name.contains("BIAS")) {
parameter.setShape(new Shape(gates * stateSize));
} else if (name.contains("i2h")) {
parameter.setShape(new Shape(gates * stateSize, inputSize));
} else if (name.contains("h2h")) {
parameter.setShape(new Shape(gates * stateSize, stateSize));
} else {
throw new IllegalArgumentException("Invalid parameter name");
}
}
}
/** {@inheritDoc} */
@Override
public void loadMetadata(byte loadVersion, DataInputStream is)
throws IOException, MalformedModelException {
if (loadVersion == version) {
readInputShapes(is);
} else if (loadVersion != 1) {
throw new MalformedModelException("Unsupported encoding version: " + loadVersion);
}
}
protected int getNumDirections() {
return bidirectional ? 2 : 1;
}
/** The Builder to construct a {@link RecurrentBlock} type of {@link ai.djl.nn.Block}. */
@SuppressWarnings("rawtypes")
public abstract static class BaseBuilder {
protected float dropRate;
protected long stateSize;
protected int numLayers;
// set it true by default for usability
protected boolean batchFirst = true;
protected boolean hasBiases = true;
protected boolean bidirectional;
protected boolean returnState;
protected RNN.Activation activation;
/**
* Sets the drop rate of the dropout on the outputs of each RNN layer, except the last
* layer.
*
* @param dropRate the drop rate of the dropout
* @return this Builder
*/
public T optDropRate(float dropRate) {
this.dropRate = dropRate;
return self();
}
/**
* Sets the Required size of the state for each layer.
*
* @param stateSize the size of the state for each layer
* @return this Builder
*/
public T setStateSize(int stateSize) {
this.stateSize = stateSize;
return self();
}
/**
* Sets the Required number of stacked layers.
*
* @param numLayers the number of stacked layers
* @return this Builder
*/
public T setNumLayers(int numLayers) {
this.numLayers = numLayers;
return self();
}
/**
* Sets the optional parameter that indicates whether to use bidirectional recurrent layers.
*
* @param useBidirectional whether to use bidirectional recurrent layers
* @return this Builder
*/
public T optBidirectional(boolean useBidirectional) {
this.bidirectional = useBidirectional;
return self();
}
/**
* Sets the optional batchFirst flag that indicates whether the input is batch major or not.
* The default value is true.
*
* @param batchFirst whether the input is batch major or not
* @return this Builder
*/
public T optBatchFirst(boolean batchFirst) {
this.batchFirst = batchFirst;
return self();
}
/**
* Sets the optional biases flag that indicates whether to use biases or not.
*
* @param hasBiases whether to use biases or not
* @return this Builder
*/
public T optHasBiases(boolean hasBiases) {
this.hasBiases = hasBiases;
return self();
}
/**
* Sets the optional flag that indicates whether to return state or not. This is typically
* useful when you use RecurrentBlock in Sequential block. The default value is false.
*
* @param returnState whether to return state or not
* @return this Builder
*/
public T optReturnState(boolean returnState) {
this.returnState = returnState;
return self();
}
protected abstract T self();
}
}