@rcurtin I have tried, but the tests fail, because the Convultion function expects three MatType; in this case, one of them is arma::col, so it does not pass the tests.
This only fails when we are passing to template function parameters.
Up to you, we can merge it now and then figure out the solution for this later, or we can find a solution right now before merging, also I do not know the reason why we are using unsafe_col instead of using col directly

I think you should be able to solve this by adding more template parameters (one for each argument, for instance). That will allow the filter to take a different type, if needed.

I would suspect that the reason unsafe_col() was being used in the first place was just to avoid this exact problem. unsafe_col() just returns a Col that is an alias of the given column, instead of a subview. If each argument is its own template parameter, it should be possible to use .col() instead of .unsafe_col().

@rcurtin This is the real reason that unsafe_col is used

const eT* kernelPtr = filter.memptr();

Since it is not a real col, we can call memptr() as if it was a matrix.
If I try to use col() instead the compiler will complain that I need to use colptr instead of memptr

I would say, let us merge it in this state, technically, we need to find a nicer implementation for these functions with bandicoot, and I do not know the answer to this, adding overloads looks really ugly, it would be nice to have a generic function that would work with both libraries

Ah. I see, thanks for digging into that. That is indeed going to be more complicated than I thought. I agree with your assessment that we should save it for later then.

I will keep it like this because we will have to refactor this anyway so that we will come back to it.
I think this will save us one instruction as I will need to convert unsafe_col back to a temporary matrix