how do you access the nonzero elements in SeqAIJ matrices
Ahmed El Zein
ahmed at azein.com
Mon Aug 4 11:09:16 CDT 2008
On Mon, 2008-08-04 at 23:13 +0800, Zi-Hao Wei wrote:
> On Mon, Aug 4, 2008 at 10:53 PM, Ahmed El Zein <ahmed at azein.com> wrote:
> > my code looks like:
> > ierr = MatCreate(PETSC_COMM_WORLD,&A); CHKERRQ(ierr);
> > ierr = MatSetSizes(A,M,N,M,N); CHKERRQ(ierr);
> > ierr = MatSetType(A, MATSEQAIJ); CHKERRQ(ierr);
> > ierr = MatAssemblyBegin(A, MAT_FINAL_ASSEMBLY); CHKERRQ(ierr);
> > [...lots of MatSetValue() calls...]
> > ierr = MatAssemblyEnd(A, MAT_FINAL_ASSEMBLY); CHKERRQ(ierr);
>
> I think that the code should be
> ierr = MatCreate(PETSC_COMM_WORLD,&A); CHKERRQ(ierr);
> ierr = MatSetSizes(A,M,N,M,N); CHKERRQ(ierr);
> ierr = MatSetType(A, MATSEQAIJ); CHKERRQ(ierr);
> [...lots of MatSetValue() calls...]
> ierr = MatAssemblyBegin(A, MAT_FINAL_ASSEMBLY); CHKERRQ(ierr);
> ierr = MatAssemblyEnd(A, MAT_FINAL_ASSEMBLY); CHKERRQ(ierr);
>
> The routines MatAssemblyBegin and MatAssemblyEnd should be called
> after completing all calls to MatSetValues().
You are right of course. But if these 2 calls are meant to be right
after each other, why isn't there just one MatAssembly() call versus a
Begin and End call?
btw fixing this did not affect the problem I had.
Ahmed
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