BLAS Level 2 band matrix-vector product multiple vectors

Question

A routine in BLAS Level 2 for banded matrix vector product exists, both for general and symmetric cases (links for MKL implementation).

cblas_?gbmv

cblas_?sbmv

Is there any way to use multiple vectors (without using an outside for-loop), to maximize performance in such cases?

Answer 1

I think that the Spike library is supposed to have such a routine for the symmetric case. I'm afraid I cannot be of any more help, though, as I have never used it.

The algorithm and implementation of Spike (for system solving) is outlined in [Polizzi & Sameh, Comp. Fluids (36), 2007].

Answer 2

AFAIK the answer is no.

The complete list of level3 BLAS subroutines can be found here

http://www.netlib.org/blas/#_level_3

and there is no banded-matrix subroutine.

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Extra information: if you are using blas/lapack & C++ there is a recent initiative to design a C++ interface:

http://www.netlib.org/na-digest-html/17/v17n21.html#1

(cblas and lapacke are more oriented for a C usage)