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package org.deeplearning4j.nn.layers;

import org.deeplearning4j.berkeley.Pair;
import org.deeplearning4j.nn.api.Layer;
import org.deeplearning4j.nn.conf.NeuralNetConfiguration;
import org.deeplearning4j.nn.gradient.DefaultGradient;
import org.deeplearning4j.nn.gradient.Gradient;
import org.nd4j.linalg.api.ndarray.INDArray;
import org.nd4j.linalg.factory.Nd4j;

/**
 * Created by davekale on 12/7/16.
 */
public class DropoutLayer extends BaseLayer {

    public DropoutLayer(NeuralNetConfiguration conf) {
        super(conf);
    }

    public DropoutLayer(NeuralNetConfiguration conf, INDArray input) {
        super(conf, input);
    }

    @Override
    public double calcL2(boolean backpropParamsOnly) {
        return 0;
    }

    @Override
    public double calcL1(boolean backpropParamsOnly) {
        return 0;
    }

    @Override
    public Type type() {
        return Type.FEED_FORWARD;
    }

    @Override
    public void fit(INDArray input) {}

    @Override
    public Pair backpropGradient(INDArray epsilon) {
        INDArray delta = epsilon.dup();

        if (maskArray != null) {
            delta.muliColumnVector(maskArray);
        }

        Gradient ret = new DefaultGradient();
        return new Pair<>(ret, delta);
    }

    @Override
    public INDArray preOutput(boolean training) {
        if (input == null) {
            throw new IllegalArgumentException("Cannot perform forward pass with null input " + layerId());
        }
        INDArray dummy = input;
        applyDropOutIfNecessary(training);

        INDArray ret;
        if (training) {
            //dup required: need to keep original input for backprop
            ret = input.dup();
        } else {
            ret = input;
        }

        if (maskArray != null) {
            ret.muliColumnVector(maskArray);
        }

        return ret;
    }

    @Override
    public INDArray activate(boolean training) {
        INDArray z = preOutput(training);
        return z;
    }

    @Override
    public Layer transpose() {
        throw new UnsupportedOperationException("Not supported - " + layerId());
    }

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


    @Override
    public Gradient calcGradient(Gradient layerError, INDArray indArray) {
        throw new UnsupportedOperationException("Not supported " + layerId());
    }

    @Override
    public void merge(Layer layer, int batchSize) {
        throw new UnsupportedOperationException("Not supported - " + layerId());
    }

    @Override
    public INDArray params() {
        return null;
    }
}