MatCreateMPIAIJ(PETSC_COMM_WORLD, PETSC_DECIDE, PETSC_DECIDE, N, M, 12, PETSC_NULL, 12, PETSC_NULL, &AT);
MatTranspose(A,MAT_IGNORE_MATRIX,&AT);

should be replaced with

MatTranspose(A,MAT_INITIAL_MATRIX,&AT);
Hm, it seems this was the reason...

With this change, do you still get different matrix product comparing with Matlab's?

I'll add an error flag in petsc to prevent using MatTranspose(A,MAT_IGNORE_MATRIX,&AT).

Do you mean 'Cm = A'*B;'?

'Cm = A.'*B;' gives component-wise matrix product, not matrix product.

.' operator means non-Hermitian transpose. That is what I get with MatTranspose (in contrast with MatHermitianTranspose)
component-wise matrix product would be .*

You are correct.

Hong

Hong
C = PetscBinaryRead('C.dat','complex',true);

Matrix C is different depending on number of cores I use.
My PETSc is:
Using Petsc Development HG revision: 876c894d95f4fa6561d0a91310ca914592527960 HG Date: Tue Jan 10 19:27:14 2012 +0100

On 06.02.2012 17:13, Hong Zhang wrote:
MatMatMult() in petsc is not well-tested for complex - could be buggy.
Can you send us the matrices A and B in petsc binary format for investigation?

Hong

On Mon, Feb 6, 2012 at 5:55 AM, Alexander Grayver <agrayver@gfz-potsdam.de> wrote:

Dear PETSc team,

I try to use:
call MatMatMult(A,B,MAT_INITIAL_MATRIX,PETSC_DEFAULT_DOUBLE_PRECISION,C,ierr);CHKERRQ(ierr)

Where both A and B are rectangular, but A is sparse and B is dense. Both are double complex and distributed.
The product PETSc gives me contains some errors in some part of the matrix.
I output A, B and C then computed product in matlab.

Attached you see figure plotted as:
imagesc(log10(abs(C-Cm)))

Where Cm -- product computed in matlab.

The pattern and amplitude vary depending on the number of cores I use. This picture is obtained for 48 cores (I've tried 12, 64 cores as well).

Where should I look for possible explanation?

--
Regards,
Alexander

-- Regards, Alexander
-- Regards, Alexander