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Java example source code file (LastTimeStepVertex.java)

This example Java source code file (LastTimeStepVertex.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

data, equalsandhashcode, graphvertex, indarray, invalidinputtypeexception, lasttimestepvertex, override, rnn, string

The LastTimeStepVertex.java Java example source code

/*
 *
 *  * Copyright 2016 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
 *  *
 *  *    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
 *  *    limitations under the License.
 *
 */

package org.deeplearning4j.nn.conf.graph.rnn;

import com.fasterxml.jackson.annotation.JsonProperty;
import lombok.Data;
import lombok.EqualsAndHashCode;
import org.deeplearning4j.nn.conf.graph.GraphVertex;
import org.deeplearning4j.nn.conf.inputs.InputType;
import org.deeplearning4j.nn.conf.inputs.InvalidInputTypeException;
import org.deeplearning4j.nn.graph.ComputationGraph;
import org.nd4j.linalg.api.ndarray.INDArray;

/** LastTimeStepVertex is used in the context of recurrent neural network activations, to go from 3d (time series)
 * activations to 2d activations, by extracting out the last time step of activations for each example.<br>
 * This can be used for example in sequence to sequence architectures, and potentially for sequence classification.
 * <b>NOTE: Because RNNs may have masking arrays (to allow for examples/time series of different lengths in the same
 * minibatch), it is necessary to provide the same of the network input that has the corresponding mask array. If this
 * input does not have a mask array, the last time step of the input will be used for all examples; otherwise, the time
 * step of the last non-zero entry in the mask array (for each example separately) will be used.
 * @author Alex Black
 */
@Data @EqualsAndHashCode(callSuper=false)
public class LastTimeStepVertex extends GraphVertex {

    private String maskArrayInputName;

    /**
     *
     * @param maskArrayInputName The name of the input to look at when determining the last time step. Specifically, the
     *                           mask array of this time series input is used when determining which time step to extract
     *                           and return.
     */
    public LastTimeStepVertex(@JsonProperty("maskArrayInputName") String maskArrayInputName){
        this.maskArrayInputName = maskArrayInputName;
    }

    @Override
    public GraphVertex clone() {
        return new LastTimeStepVertex(maskArrayInputName);
    }

    @Override
    public boolean equals(Object o) {
        if(!(o instanceof LastTimeStepVertex)) return false;
        LastTimeStepVertex ltsv = (LastTimeStepVertex)o;
        if(maskArrayInputName == null && ltsv.maskArrayInputName != null || maskArrayInputName != null && ltsv.maskArrayInputName == null) return false;
        return maskArrayInputName == null || maskArrayInputName.equals(ltsv.maskArrayInputName);
    }

    @Override
    public int hashCode() {
        return (maskArrayInputName == null ? 452766971 : maskArrayInputName.hashCode());
    }

    @Override
    public int numParams(boolean backprop){
        return 0;
    }

    @Override
    public org.deeplearning4j.nn.graph.vertex.impl.rnn.LastTimeStepVertex instantiate(ComputationGraph graph, String name, int idx,
                                                                                      INDArray paramsView, boolean initializeParams) {
        return new org.deeplearning4j.nn.graph.vertex.impl.rnn.LastTimeStepVertex(graph,name,idx,maskArrayInputName);
    }

    @Override
    public InputType getOutputType(InputType... vertexInputs) throws InvalidInputTypeException {
        if(vertexInputs.length != 1) throw new InvalidInputTypeException("Invalid input type: cannot get last time step of more than 1 input");
        if(vertexInputs[0].getType() != InputType.Type.RNN){
            throw new InvalidInputTypeException("Invalid input type: cannot get subset of non RNN input (got: " + vertexInputs[0] + ")");
        }

        return InputType.feedForward(((InputType.InputTypeRecurrent)vertexInputs[0]).getSize());
    }

    @Override
    public String toString(){
        return "LastTimeStepVertex(inputName="+maskArrayInputName+")";
    }
}

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