/// <summary>
/// Merge the given
/// <c>Cost</c>
/// data with the data in this
/// instance.
/// </summary>
/// <param name="otherCost"/>
public virtual void Merge(Classifier.Cost otherCost)
{
this.cost += otherCost.GetCost();
this.percentCorrect += otherCost.GetPercentCorrect();
ArrayMath.AddInPlace(this.gradW1, otherCost.GetGradW1());
ArrayMath.PairwiseAddInPlace(this.gradb1, otherCost.GetGradb1());
ArrayMath.AddInPlace(this.gradW2, otherCost.GetGradW2());
ArrayMath.AddInPlace(this.gradE, otherCost.GetGradE());
}
/// <summary>
/// Determine the total cost on the dataset associated with this
/// classifier using the current learned parameters.
/// </summary>
/// <remarks>
/// Determine the total cost on the dataset associated with this
/// classifier using the current learned parameters. This cost is
/// evaluated using mini-batch adaptive gradient descent.
/// This method launches multiple threads, each of which evaluates
/// training cost on a partition of the mini-batch.
/// </remarks>
/// <param name="batchSize"/>
/// <param name="regParameter">Regularization parameter (lambda)</param>
/// <param name="dropOutProb">
/// Drop-out probability. Hidden-layer units in the
/// neural network will be randomly turned off
/// while training a particular example with this
/// probability.
/// </param>
/// <returns>
/// A
/// <see cref="Cost"/>
/// object which describes the total cost of the given
/// weights, and includes gradients to be used for further
/// training
/// </returns>
public virtual Classifier.Cost ComputeCostFunction(int batchSize, double regParameter, double dropOutProb)
{
ValidateTraining();
IList <Example> examples = Edu.Stanford.Nlp.Parser.Nndep.Util.GetRandomSubList(dataset.examples, batchSize);
// Redo precomputations for only those features which are triggered
// by examples in this mini-batch.
ICollection <int> toPreCompute = GetToPreCompute(examples);
PreCompute(toPreCompute);
// Set up parameters for feedforward
Classifier.FeedforwardParams @params = new Classifier.FeedforwardParams(batchSize, dropOutProb);
// Zero out saved-embedding gradients
gradSaved = new double[][] { };
int numChunks = config.trainingThreads;
IList <IList <Example> > chunks = CollectionUtils.PartitionIntoFolds(examples, numChunks);
// Submit chunks for processing on separate threads
foreach (ICollection <Example> chunk in chunks)
{
jobHandler.Put(new Pair <ICollection <Example>, Classifier.FeedforwardParams>(chunk, @params));
}
jobHandler.Join(false);
// Join costs from each chunk
Classifier.Cost cost = null;
while (jobHandler.Peek())
{
Classifier.Cost otherCost = jobHandler.Poll();
if (cost == null)
{
cost = otherCost;
}
else
{
cost.Merge(otherCost);
}
}
if (cost == null)
{
return(null);
}
// Backpropagate gradients on saved pre-computed values to actual
// embeddings
cost.BackpropSaved(toPreCompute);
cost.AddL2Regularization(regParameter);
return(cost);
}
/// <summary>
/// Update classifier weights using the given training cost
/// information.
/// </summary>
/// <param name="cost">
/// Cost information as returned by
/// <see cref="ComputeCostFunction(int, double, double)"/>
/// .
/// </param>
/// <param name="adaAlpha">Global AdaGrad learning rate</param>
/// <param name="adaEps">
/// Epsilon value for numerical stability in AdaGrad's
/// division
/// </param>
public virtual void TakeAdaGradientStep(Classifier.Cost cost, double adaAlpha, double adaEps)
{
ValidateTraining();
double[][] gradW1 = cost.GetGradW1();
double[][] gradW2 = cost.GetGradW2();
double[][] gradE = cost.GetGradE();
double[] gradb1 = cost.GetGradb1();
for (int i = 0; i < W1.Length; ++i)
{
for (int j = 0; j < W1[i].Length; ++j)
{
eg2W1[i][j] += gradW1[i][j] * gradW1[i][j];
W1[i][j] -= adaAlpha * gradW1[i][j] / System.Math.Sqrt(eg2W1[i][j] + adaEps);
}
}
for (int i_1 = 0; i_1 < b1.Length; ++i_1)
{
eg2b1[i_1] += gradb1[i_1] * gradb1[i_1];
b1[i_1] -= adaAlpha * gradb1[i_1] / System.Math.Sqrt(eg2b1[i_1] + adaEps);
}
for (int i_2 = 0; i_2 < W2.Length; ++i_2)
{
for (int j = 0; j < W2[i_2].Length; ++j)
{
eg2W2[i_2][j] += gradW2[i_2][j] * gradW2[i_2][j];
W2[i_2][j] -= adaAlpha * gradW2[i_2][j] / System.Math.Sqrt(eg2W2[i_2][j] + adaEps);
}
}
if (config.doWordEmbeddingGradUpdate)
{
for (int i_3 = 0; i_3 < E.Length; ++i_3)
{
for (int j = 0; j < E[i_3].Length; ++j)
{
eg2E[i_3][j] += gradE[i_3][j] * gradE[i_3][j];
E[i_3][j] -= adaAlpha * gradE[i_3][j] / System.Math.Sqrt(eg2E[i_3][j] + adaEps);
}
}
}
}