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package org.deeplearning4j.util;

import org.deeplearning4j.nn.api.Layer;
import org.nd4j.linalg.api.ndarray.INDArray;
import org.nd4j.linalg.api.shape.Shape;
import org.nd4j.linalg.factory.Nd4j;


/**
 * @author Adam Gibson
 */
public class Dropout {

    /**
     * Apply drop connect to the given variable
     * @param layer the layer with the variables
     * @param variable the variable to apply
     * @return the post applied drop connect
     */
    public static INDArray applyDropConnect(Layer layer,String variable) {
        return layer.getParam(variable).mul(Nd4j.getDistributions().createBinomial(1,layer.conf().getLayer().getDropOut()).sample(layer.getParam(variable).shape()));
    }

    /**
     * Apply dropout to the given input
     * and return the drop out mask used
     * @param input the input to do drop out on
     * @param dropout the drop out probability
     * @param dropoutMask the dropout mask applied (can be null)
     * @return the dropout mask used
     */
    public static INDArray applyDropout(INDArray input,double dropout,INDArray dropoutMask) {
        if(dropoutMask == null || !Shape.shapeEquals(input.shape(), dropoutMask.shape())) {
            dropoutMask = Nd4j.getDistributions().createBinomial(1,dropout).sample(input.shape()).divi(dropout);
        }

        input.muli(dropoutMask);
        return dropoutMask;
    }


}