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Java example source code file (ElementWiseVertex.java)

This example Java source code file (ElementWiseVertex.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

add, cannot, elementwisevertex, illegalstateexception, indarray, not, override, pair, product, string, subtract, unknown, unsupportedoperationexception, vertexindices

The ElementWiseVertex.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.graph.vertex.impl;

import org.deeplearning4j.berkeley.Pair;
import org.deeplearning4j.nn.api.Layer;
import org.deeplearning4j.nn.gradient.Gradient;
import org.deeplearning4j.nn.graph.ComputationGraph;
import org.deeplearning4j.nn.graph.vertex.BaseGraphVertex;
import org.deeplearning4j.nn.graph.vertex.VertexIndices;
import org.nd4j.linalg.api.ndarray.INDArray;

/** An ElementWiseVertex is used to combine the activations of two or more layer in an element-wise manner<br>
 * For example, the activations may be combined by addition, subtraction or multiplication.
 * Addition may use an arbitrary number of input arrays. Note that in the case of subtraction, only two inputs may be used.
 * In all cases, the shape of the input arrays must be identical.
 * @author Alex Black
 */
public class ElementWiseVertex extends BaseGraphVertex {

    public enum Op {Add, Subtract, Product};

    private Op op;
    private int nInForwardPass;

    public ElementWiseVertex(ComputationGraph graph, String name, int vertexIndex, Op op){
        this(graph,name,vertexIndex,null,null,op);
    }

    public ElementWiseVertex(ComputationGraph graph, String name, int vertexIndex, VertexIndices[] inputVertices, VertexIndices[] outputVertices, Op op) {
        super(graph, name, vertexIndex, inputVertices, outputVertices);
        this.op = op;
    }

    @Override
    public boolean hasLayer() {
        return false;
    }

    @Override
    public boolean isOutputVertex() {
        return false;
    }

    @Override
    public Layer getLayer() {
        return null;
    }

    @Override
    public INDArray doForward(boolean training) {
        if(!canDoForward()) throw new IllegalStateException("Cannot do forward pass: inputs not set");

        nInForwardPass = inputs.length;
        if(inputs.length == 1) return inputs[0];

        switch(op){
            case Add:
                INDArray sum = inputs[0].dup();
                for( int i=1; i<inputs.length; i++){
                    sum.addi(inputs[i]);
                }
                return sum;
            case Subtract:
                if(inputs.length != 2) throw new IllegalArgumentException("ElementWise subtraction only supports 2 inputs");
                return inputs[0].sub(inputs[1]);
            case Product:
                throw new UnsupportedOperationException("ElementWise product: Not yet implemented");
            default:
                throw new UnsupportedOperationException("Unknown op: " + op);
        }
    }

    @Override
    public Pair<Gradient, INDArray[]> doBackward(boolean tbptt) {
        if(!canDoBackward()) throw new IllegalStateException("Cannot do backward pass: errors not set");

        if(nInForwardPass == 1) return new Pair<>(null,epsilons);

        switch(op){
            case Add:
                //If x=sum_i a_i then dL/da_i = dL/dx * dx/da_i = dL/dx
                INDArray[] out = new INDArray[nInForwardPass];
                out[0] = epsilons[0];
                for( int i=1; i<nInForwardPass; i++ ) out[i] = out[0].dup();
                return new Pair<>(null,out);
            case Subtract:
                INDArray[] out2 = new INDArray[2];
                out2[0] = epsilons[0];
                out2[1] = epsilons[0].mul(-1);
                return new Pair<>(null,out2);
            case Product:
                throw new UnsupportedOperationException("Not yet implemented");
            default:
                throw new UnsupportedOperationException("Unknown op: " + op);
        }
    }

    @Override
    public void setBackpropGradientsViewArray(INDArray backpropGradientsViewArray) {
        if(backpropGradientsViewArray != null) throw new RuntimeException("Vertex does not have gradients; gradients view array cannot be set here");
    }

    @Override
    public String toString() {
        return "ElementWiseVertex(id=" + this.getVertexIndex() + ",name=\"" + this.getVertexName() + "\",op=" + op + ")";
    }
}

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