org.deeplearning4j.nn.layers.recurrent.GravesLSTM Maven / Gradle / Ivy
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*
* * Copyright 2015 Skymind,Inc.
* *
* * Licensed under the Apache License, Version 2.0 (the "License");
* * you may not use this file except in compliance with the License.
* * You may obtain a copy of the License at
* *
* * http://www.apache.org/licenses/LICENSE-2.0
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* * Unless required by applicable law or agreed to in writing, software
* * distributed under the License 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
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package org.deeplearning4j.nn.layers.recurrent;
import org.deeplearning4j.berkeley.Pair;
import org.deeplearning4j.nn.api.Layer;
import org.deeplearning4j.nn.api.MaskState;
import org.deeplearning4j.nn.conf.NeuralNetConfiguration;
import org.deeplearning4j.nn.gradient.Gradient;
import org.deeplearning4j.nn.params.GravesLSTMParamInitializer;
import org.nd4j.linalg.api.ndarray.INDArray;
import java.util.Map;
/**
* LSTM layer implementation.
* Based on Graves: Supervised Sequence Labelling with Recurrent Neural Networks
* http://www.cs.toronto.edu/~graves/phd.pdf
* See also for full/vectorized equations (and a comparison to other LSTM variants):
* Greff et al. 2015, "LSTM: A Search Space Odyssey", pg11. This is the "vanilla" variant in said paper
* http://arxiv.org/pdf/1503.04069.pdf
*
* @author Alex Black
*/
public class GravesLSTM extends BaseRecurrentLayer {
public static final String STATE_KEY_PREV_ACTIVATION = "prevAct";
public static final String STATE_KEY_PREV_MEMCELL = "prevMem";
public GravesLSTM(NeuralNetConfiguration conf) {
super(conf);
}
public GravesLSTM(NeuralNetConfiguration conf, INDArray input) {
super(conf, input);
}
@Override
public Gradient gradient() {
throw new UnsupportedOperationException(
"gradient() method for layerwise pretraining: not supported for LSTMs (pretraining not possible)");
}
@Override
public Gradient calcGradient(Gradient layerError, INDArray activation) {
throw new UnsupportedOperationException("Not supported");
}
@Override
public Pair backpropGradient(INDArray epsilon) {
return backpropGradientHelper(epsilon, false, -1);
}
@Override
public Pair tbpttBackpropGradient(INDArray epsilon, int tbpttBackwardLength) {
return backpropGradientHelper(epsilon, true, tbpttBackwardLength);
}
private Pair backpropGradientHelper(final INDArray epsilon, final boolean truncatedBPTT,
final int tbpttBackwardLength) {
final INDArray inputWeights = getParam(GravesLSTMParamInitializer.INPUT_WEIGHT_KEY);
final INDArray recurrentWeights = getParam(GravesLSTMParamInitializer.RECURRENT_WEIGHT_KEY); //Shape: [hiddenLayerSize,4*hiddenLayerSize+3]; order: [wI,wF,wO,wG,wFF,wOO,wGG]
//First: Do forward pass to get gate activations, zs etc.
FwdPassReturn fwdPass;
if (truncatedBPTT) {
fwdPass = activateHelper(true, stateMap.get(STATE_KEY_PREV_ACTIVATION),
stateMap.get(STATE_KEY_PREV_MEMCELL), true);
//Store last time step of output activations and memory cell state in tBpttStateMap
tBpttStateMap.put(STATE_KEY_PREV_ACTIVATION, fwdPass.lastAct);
tBpttStateMap.put(STATE_KEY_PREV_MEMCELL, fwdPass.lastMemCell);
} else {
fwdPass = activateHelper(true, null, null, true);
}
return LSTMHelpers.backpropGradientHelper(this.conf, this.layerConf().getGateActivationFn(), this.input,
recurrentWeights, inputWeights, epsilon, truncatedBPTT, tbpttBackwardLength, fwdPass, true,
GravesLSTMParamInitializer.INPUT_WEIGHT_KEY, GravesLSTMParamInitializer.RECURRENT_WEIGHT_KEY,
GravesLSTMParamInitializer.BIAS_KEY, gradientViews, null);
}
@Override
public INDArray preOutput(INDArray x) {
return activate(x, true);
}
@Override
public INDArray preOutput(INDArray x, boolean training) {
return activate(x, training);
}
@Override
public INDArray activate(INDArray input, boolean training) {
setInput(input);
return activateHelper(training, null, null, false).fwdPassOutput;
}
@Override
public INDArray activate(INDArray input) {
setInput(input);
return activateHelper(true, null, null, false).fwdPassOutput;
}
@Override
public INDArray activate(boolean training) {
return activateHelper(training, null, null, false).fwdPassOutput;
}
@Override
public INDArray activate() {
return activateHelper(false, null, null, false).fwdPassOutput;
}
private FwdPassReturn activateHelper(final boolean training, final INDArray prevOutputActivations,
final INDArray prevMemCellState, boolean forBackprop) {
final INDArray recurrentWeights = getParam(GravesLSTMParamInitializer.RECURRENT_WEIGHT_KEY); //Shape: [hiddenLayerSize,4*hiddenLayerSize+3]; order: [wI,wF,wO,wG,wFF,wOO,wGG]
final INDArray inputWeights = getParam(GravesLSTMParamInitializer.INPUT_WEIGHT_KEY); //Shape: [n^(L-1),4*hiddenLayerSize]; order: [wi,wf,wo,wg]
final INDArray biases = getParam(GravesLSTMParamInitializer.BIAS_KEY); //by row: IFOG //Shape: [4,hiddenLayerSize]; order: [bi,bf,bo,bg]^T
return LSTMHelpers.activateHelper(this, this.conf, this.layerConf().getGateActivationFn(), this.input,
recurrentWeights, inputWeights, biases, training, prevOutputActivations, prevMemCellState,
forBackprop, true, GravesLSTMParamInitializer.INPUT_WEIGHT_KEY, null);
}
@Override
public INDArray activationMean() {
return activate();
}
@Override
public Type type() {
return Type.RECURRENT;
}
@Override
public Layer transpose() {
throw new UnsupportedOperationException("Not supported");
}
@Override
public boolean isPretrainLayer() {
return false;
}
@Override
public Pair feedForwardMaskArray(INDArray maskArray, MaskState currentMaskState,
int minibatchSize) {
//LSTM (standard, not bi-directional) don't make any changes to the data OR the mask arrays
//Any relevant masking occurs during backprop
//They also set the current mask array as inactive: this is for situations like the following:
// in -> dense -> lstm -> dense -> lstm
// The first dense should be masked using the input array, but the second shouldn't. If necessary, the second
// dense will be masked via the output layer mask
return new Pair<>(maskArray, MaskState.Passthrough);
}
@Override
public double calcL2(boolean backpropParamsOnly) {
if (!conf.isUseRegularization())
return 0.0;
double l2Sum = 0.0;
for (Map.Entry entry : paramTable().entrySet()) {
double l2 = conf.getL2ByParam(entry.getKey());
if (l2 > 0) {
double norm2 = getParam(entry.getKey()).norm2Number().doubleValue();
l2Sum += 0.5 * l2 * norm2 * norm2;
}
}
return l2Sum;
}
@Override
public double calcL1(boolean backpropParamsOnly) {
if (!conf.isUseRegularization())
return 0.0;
double l1Sum = 0.0;
for (Map.Entry entry : paramTable().entrySet()) {
double l1 = conf.getL1ByParam(entry.getKey());
if (l1 > 0) {
double norm1 = getParam(entry.getKey()).norm1Number().doubleValue();
l1Sum += l1 * norm1;
}
}
return l1Sum;
}
@Override
public INDArray rnnTimeStep(INDArray input) {
setInput(input);
FwdPassReturn fwdPass = activateHelper(false, stateMap.get(STATE_KEY_PREV_ACTIVATION),
stateMap.get(STATE_KEY_PREV_MEMCELL), false);
INDArray outAct = fwdPass.fwdPassOutput;
//Store last time step of output activations and memory cell state for later use:
stateMap.put(STATE_KEY_PREV_ACTIVATION, fwdPass.lastAct);
stateMap.put(STATE_KEY_PREV_MEMCELL, fwdPass.lastMemCell);
return outAct;
}
@Override
public INDArray rnnActivateUsingStoredState(INDArray input, boolean training, boolean storeLastForTBPTT) {
setInput(input);
FwdPassReturn fwdPass = activateHelper(training, stateMap.get(STATE_KEY_PREV_ACTIVATION),
stateMap.get(STATE_KEY_PREV_MEMCELL), false);
INDArray outAct = fwdPass.fwdPassOutput;
if (storeLastForTBPTT) {
//Store last time step of output activations and memory cell state in tBpttStateMap
tBpttStateMap.put(STATE_KEY_PREV_ACTIVATION, fwdPass.lastAct);
tBpttStateMap.put(STATE_KEY_PREV_MEMCELL, fwdPass.lastMemCell);
}
return outAct;
}
}
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