/// <summary>Applies the derivative of tanh to each of the elements in the vector.</summary>
/// <remarks>Applies the derivative of tanh to each of the elements in the vector. Returns a new matrix.</remarks>
public static SimpleMatrix ElementwiseApplyTanhDerivative(SimpleMatrix input)
{
SimpleMatrix output = new SimpleMatrix(input.NumRows(), input.NumCols());
output.Set(1.0);
output = output.Minus(input.ElementMult(input));
return(output);
}
private void BackpropDerivativesAndError(Tree tree, TwoDimensionalMap <string, string, SimpleMatrix> binaryTD, TwoDimensionalMap <string, string, SimpleMatrix> binaryCD, TwoDimensionalMap <string, string, SimpleTensor> binaryTensorTD, IDictionary
<string, SimpleMatrix> unaryCD, IDictionary <string, SimpleMatrix> wordVectorD, SimpleMatrix deltaUp)
{
if (tree.IsLeaf())
{
return;
}
SimpleMatrix currentVector = RNNCoreAnnotations.GetNodeVector(tree);
string category = tree.Label().Value();
category = model.BasicCategory(category);
// Build a vector that looks like 0,0,1,0,0 with an indicator for the correct class
SimpleMatrix goldLabel = new SimpleMatrix(model.numClasses, 1);
int goldClass = RNNCoreAnnotations.GetGoldClass(tree);
if (goldClass >= 0)
{
goldLabel.Set(goldClass, 1.0);
}
double nodeWeight = model.op.trainOptions.GetClassWeight(goldClass);
SimpleMatrix predictions = RNNCoreAnnotations.GetPredictions(tree);
// If this is an unlabeled class, set deltaClass to 0. We could
// make this more efficient by eliminating various of the below
// calculations, but this would be the easiest way to handle the
// unlabeled class
SimpleMatrix deltaClass = goldClass >= 0 ? predictions.Minus(goldLabel).Scale(nodeWeight) : new SimpleMatrix(predictions.NumRows(), predictions.NumCols());
SimpleMatrix localCD = deltaClass.Mult(NeuralUtils.ConcatenateWithBias(currentVector).Transpose());
double error = -(NeuralUtils.ElementwiseApplyLog(predictions).ElementMult(goldLabel).ElementSum());
error = error * nodeWeight;
RNNCoreAnnotations.SetPredictionError(tree, error);
if (tree.IsPreTerminal())
{
// below us is a word vector
unaryCD[category] = unaryCD[category].Plus(localCD);
string word = tree.Children()[0].Label().Value();
word = model.GetVocabWord(word);
//SimpleMatrix currentVectorDerivative = NeuralUtils.elementwiseApplyTanhDerivative(currentVector);
//SimpleMatrix deltaFromClass = model.getUnaryClassification(category).transpose().mult(deltaClass);
//SimpleMatrix deltaFull = deltaFromClass.extractMatrix(0, model.op.numHid, 0, 1).plus(deltaUp);
//SimpleMatrix wordDerivative = deltaFull.elementMult(currentVectorDerivative);
//wordVectorD.put(word, wordVectorD.get(word).plus(wordDerivative));
SimpleMatrix currentVectorDerivative = NeuralUtils.ElementwiseApplyTanhDerivative(currentVector);
SimpleMatrix deltaFromClass = model.GetUnaryClassification(category).Transpose().Mult(deltaClass);
deltaFromClass = deltaFromClass.ExtractMatrix(0, model.op.numHid, 0, 1).ElementMult(currentVectorDerivative);
SimpleMatrix deltaFull = deltaFromClass.Plus(deltaUp);
SimpleMatrix oldWordVectorD = wordVectorD[word];
if (oldWordVectorD == null)
{
wordVectorD[word] = deltaFull;
}
else
{
wordVectorD[word] = oldWordVectorD.Plus(deltaFull);
}
}
else
{
// Otherwise, this must be a binary node
string leftCategory = model.BasicCategory(tree.Children()[0].Label().Value());
string rightCategory = model.BasicCategory(tree.Children()[1].Label().Value());
if (model.op.combineClassification)
{
unaryCD[string.Empty] = unaryCD[string.Empty].Plus(localCD);
}
else
{
binaryCD.Put(leftCategory, rightCategory, binaryCD.Get(leftCategory, rightCategory).Plus(localCD));
}
SimpleMatrix currentVectorDerivative = NeuralUtils.ElementwiseApplyTanhDerivative(currentVector);
SimpleMatrix deltaFromClass = model.GetBinaryClassification(leftCategory, rightCategory).Transpose().Mult(deltaClass);
deltaFromClass = deltaFromClass.ExtractMatrix(0, model.op.numHid, 0, 1).ElementMult(currentVectorDerivative);
SimpleMatrix deltaFull = deltaFromClass.Plus(deltaUp);
SimpleMatrix leftVector = RNNCoreAnnotations.GetNodeVector(tree.Children()[0]);
SimpleMatrix rightVector = RNNCoreAnnotations.GetNodeVector(tree.Children()[1]);
SimpleMatrix childrenVector = NeuralUtils.ConcatenateWithBias(leftVector, rightVector);
SimpleMatrix W_df = deltaFull.Mult(childrenVector.Transpose());
binaryTD.Put(leftCategory, rightCategory, binaryTD.Get(leftCategory, rightCategory).Plus(W_df));
SimpleMatrix deltaDown;
if (model.op.useTensors)
{
SimpleTensor Wt_df = GetTensorGradient(deltaFull, leftVector, rightVector);
binaryTensorTD.Put(leftCategory, rightCategory, binaryTensorTD.Get(leftCategory, rightCategory).Plus(Wt_df));
deltaDown = ComputeTensorDeltaDown(deltaFull, leftVector, rightVector, model.GetBinaryTransform(leftCategory, rightCategory), model.GetBinaryTensor(leftCategory, rightCategory));
}
else
{
deltaDown = model.GetBinaryTransform(leftCategory, rightCategory).Transpose().Mult(deltaFull);
}
SimpleMatrix leftDerivative = NeuralUtils.ElementwiseApplyTanhDerivative(leftVector);
SimpleMatrix rightDerivative = NeuralUtils.ElementwiseApplyTanhDerivative(rightVector);
SimpleMatrix leftDeltaDown = deltaDown.ExtractMatrix(0, deltaFull.NumRows(), 0, 1);
SimpleMatrix rightDeltaDown = deltaDown.ExtractMatrix(deltaFull.NumRows(), deltaFull.NumRows() * 2, 0, 1);
BackpropDerivativesAndError(tree.Children()[0], binaryTD, binaryCD, binaryTensorTD, unaryCD, wordVectorD, leftDerivative.ElementMult(leftDeltaDown));
BackpropDerivativesAndError(tree.Children()[1], binaryTD, binaryCD, binaryTensorTD, unaryCD, wordVectorD, rightDerivative.ElementMult(rightDeltaDown));
}
}
