Function cusparse_spgemm 

pub fn cusparse_spgemm(
    handle: &CusparseCompatHandle,
    a: &HostCsr,
    b: &HostCsr,
) -> SparseResult<HostCsr>

Computes the sparse-sparse product C = A * B, mirroring cusparseSpGEMM.

Delegates to HostCsr::matmul, the crate’s Gustavson SpGEMM, returning a freshly allocated HostCsr with sorted column indices per row.

Errors

Returns SparseError::DimensionMismatch if A.ncols != B.nrows.