private Mx leftContract(final Mx original) {
final VecBasedMx contracted = new VecBasedMx(original.rows(), original.columns() - 1);
for (int i = 0; i < contracted.rows(); i++) {
for (int j = 0; j < contracted.columns(); j++) {
contracted.set(i, j, original.get(i, j + 1));
}
}
return contracted;
}
public void backward() {
Mx cnc = null;
if (bias_b != 0) {
cnc = leftContract(output);
} else {
cnc = VecTools.copy(output);
}
difference = MxTools.multiply(MxTools.transpose(cnc), activations);
for (int i = 0; i < difference.dim(); i++) {
difference.set(i, difference.get(i) / activations.rows());
}
input = MxTools.multiply(cnc, weights);
rectifier.grad(activations, activations);
for (int i = 0; i < input.dim(); i++) {
input.set(i, input.get(i) * activations.get(i));
if (dropoutFraction > 0) {
input.set(i, input.get(i) * dropoutMask.get(i));
}
}
}
private Mx leftExtend(final Mx original) {
final VecBasedMx extended = new VecBasedMx(original.rows(), original.columns() + 1);
for (int i = 0; i < original.rows(); i++) {
extended.set(i, 0, bias);
}
for (int i = 0; i < original.rows(); i++) {
for (int j = 1; j < original.columns() + 1; j++) {
extended.set(i, j, original.get(i, j - 1));
}
}
return extended;
}
public void forward() {
if (bias != 0) {
activations = leftExtend(input);
} else {
activations = VecTools.copy(input);
}
output = MxTools.multiply(activations, MxTools.transpose(weights));
rectifier.value(output, output);
if (dropoutFraction > 0) {
if (isTrain) {
dropoutMask = getDropoutMask();
for (int i = 0; i < output.dim(); i++) {
output.set(i, output.get(i) * dropoutMask.get(i));
}
} else {
for (int i = 0; i < output.dim(); i++) {
output.set(i, output.get(i) * (1 - dropoutFraction));
}
}
}
}