further about PCComputeExplicitOperator()

Yujie recrusader at gmail.com
Thu May 1 19:08:25 CDT 2008

when 1 processor is used, the matrix M in PCComputeExplicitOperator(pc,&M)
uses MATSEQDENSE type. Now, I want to use MATSEQAIJ, I change the codes as
1563 if (size == 1) {
1564 //05/01/08
1565 //ierr = MatSetType(*mat,MATSEQDENSE);CHKERRQ(ierr);
1566 //ierr = MatSeqDenseSetPreallocation(*mat,PETSC_NULL);CHKERRQ(ierr);
1567 ierr = MatSetType(*mat,MATSEQAIJ);CHKERRQ(ierr);
1568 ierr = MatSeqAIJSetPreallocation(*mat,0,PETSC_NULL);CHKERRQ(ierr);
1570 } else {
1571 ierr = MatSetType(*mat,MATMPIAIJ);CHKERRQ(ierr);
1572 ierr =
1573 }

PCApply is fast when running. However,  MatSetValues() is very very slow
when some arraies need to set. I find that the problem likely lies in
in MatSetValues_SeqAIJ() after debugging the codes.
I can't further figure out where is the problem. Because it is
difficult to debug. Could you give me some advice? thanks a lot.

the version of PETSc is 2.3.3-p8.

thanks a lot.

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