Iterator<DoubleVectorElement> featureIterator = feature
.iterateNonZero();
while (featureIterator.hasNext()) {
DoubleVectorElement next = featureIterator.next();
DoubleVector rowVector = theta.getRowVector(next.getIndex());
double l2 = rowVector.pow(2d).sum();
Iterator<DoubleVectorElement> diffIterator = activationDifference
.iterateNonZero();
while (diffIterator.hasNext()) {
DoubleVectorElement diffElement = diffIterator.next();
double val = rowVector.get(diffElement.getIndex());