I have two relatively big matrices in dense format (size 100,000 * 2000), the second one being filled by zeros, except for a few hundred rows which are full (and I know which ones), and I need to add the second matrix to the first one in an efficient way.

I had a look at cusparse, but I feel that it would be more convenient to just do a loop of standard cublas rather than to bother changing the way I store the matrices to then do the updates.

What is the recommended solution in that case?