Computes binary classification accuracy of the minibatch.
Parameters:
y (Variable) – Variable holding a matrix whose i-th element
indicates the score of positive at the i-th example.
t (Variable) – Variable holding an int32 vector of ground truth labels.
If t[i]==-1, corresponding x[i] is ignored.
Accuracy is zero if all ground truth labels are -1.
Returns:
A variable holding a scalar array of the accuracy.