*/
private DenseDoubleMatrix[] getZeroWeightMatrices() {
DenseDoubleMatrix[] weightUpdateCache = new DenseDoubleMatrix[this.layerSizeArray.length - 1];
// initialize weight matrix each layer
for (int i = 0; i < weightUpdateCache.length; ++i) {
weightUpdateCache[i] = new DenseDoubleMatrix(this.layerSizeArray[i] + 1,
this.layerSizeArray[i + 1]);
}
return weightUpdateCache;
}