Question about mkl_?csrgemv

[Heo__Jun-Yeong]

Hi, when I read reference manual of mkl, the mkl_?csrgemv routine calculates y=Ax (or y=A'x) where A is m-by-m matrix in 3-array CSR format.

However, when I tested, I figured out that this routine also works well in m-by-k matrix (both k<m and k>m).

Also, proper results are obtained even when I set ja and a not in order.

 ex) for 2-by-2 matrix, [(1, 2), (3, 4)], I set ja(1)=2, a(1)=2, ja(2)=1, a(2)=1, ...

Does this routine updated in recent version?

[mecej4]

Some of the stated restrictions become understandable only if you consider that the routine in question can be asked to compute A^Tx or A.x, depending on the value of the UPLO argument. Unlike in the dense case, obtaining the CSR representation of A^T, given A in the same representation, is not entirely trivial.

I sometimes feel that it would have been better to have separate routines for computing A.x and A^Tx when A is a sparse matrix in CSR or CSC format. With COO, things are simpler since all that needs to be done is to interchange row and column indices of nonzero entries.

[Spencer_P_Intel]

Also please note that these functions have been marked deprecated since mkl 2018 update 2 release.  They have been replaced by the Sparse Blas Inspector Executor functions (https://software.intel.com/en-us/mkl-developer-reference-c-inspector-executor-sparse-blas-routines ) which provide much more opportunity to improve performance.

For instance the new function call would be using the function

mkl_sparse_?_mv(...)   (https://software.intel.com/en-us/mkl-developer-reference-c-mkl-sparse-mv)

which can optionally be preceded by some optimization hints for even faster performance using

mkl_sparse_set_mv_hint(...) (https://software.intel.com/en-us/mkl-developer-reference-c-mkl-sparse-mv ) and then mkl_sparse_optimize(...) (https://software.intel.com/en-us/mkl-developer-reference-c-mkl-sparse-optimize ).

This setup will take in all sorts of size matrices and the hints provided allow the mkl_sparse_optimize(...) to make some decisions for internal data storage that will provide improved performance of the mv (or which ever operation hints were provided) operation.