I am performing several matrix multiplications of an NxN sparse (~1-2%) matrix, let\'s call it B, with an NxM dense matrix, let\'s call it A (where M < N). N is large, as
MATLAB already uses SuiteSparse by Tim Davis for many of its operation on sparse matrices (for example see here), but neither of which I believe are multithreaded.
Usually computations on sparse matrices are memory-bound rather than CPU-bound. So even you use a multithreaded library, I doubt you will see huge benefits in terms of performance, at least not comparable to those specialized in dense matrices...
After all that the design of sparse matrices have different goals in mind than regular dense matrices, where efficient memory storage is often more important.
I did a quick search online, and found a few implementations out there: