Error in using SGEMM

Help
1

Hi all.

I wish to multiply two matrices Jr^T and Jr using the BLAS function SGEMM. Here Jr is an m x n matrix.

call sgemm('T','N',n,n,m,1.0,Jr,n,Jr,m,0.0,C,n)

While running my code on the terminal, I get the following error:

** On entry to SGEMM parameter number 8 had an illegal value

Can anyone help me identify where I might have gone wrong?

Thank you.

2

Parameter 8 (and 10) are the leading dimensions of the matrix, they are independent of the transpose option in the first and second argument.

call sgemm('T','N',n,n,m,1.0,Jr,n,Jr,m,0.0,C,n)
!                               ^    - actual leading dimension
!                               |
!                               incorrect size, should be size(Jr, 1)

Setting up calls to BLAS can be tedious to setup, I created a collection of interfaces to all BLAS routines plus convenience wrappers to set the dimension values automatically.

This should allow you to simply use

use blas, only : blas_gemm
! ...
call blas_gemm(Jr, Jr, C, transa="T")

instead of the full BLAS call.

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3

Oh. Now I understand where I had gone wrong.

I would definitely try out the BLAS wrappers as well. They seem very convenient.

Thank you.

4

Seems interesting. I see there are wrappers for both blas and lapack. blas-interface and lapack interface.

Are there some test examples available to confirm that the parameters/variables are correctly passed? Although, I am expected to test some routines in the future using these interfaces.

5

The BLAS interface is in use in several of our projects, mainly as copy rather than as proper dependency. The LAPACK interface was only assembled recently, I still have to do some testing to ensure they all work properly.

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