How to find indices with zero values?

Hi,

I have a vector Expression of dimension (ds, 1). Is there any way to find the indices having zero values in this Expression, or to check if a value in it is equal to zero? The first would be most preferable. What if the expression is batched?

Using cg.forward() followed by as_vector and comparing after that for zeros would slow down computation during training in my opinion.

Start by reviewing the DyNet Expression API and the cg.forward() and as_vector() paths mentioned in the issue, including how batched expressions are represented. Determine whether zero-value indices or equality checks are currently supported and define the expected behavior for batched expressions before estimating an implementation.

Written by the indexing model from the issue text.