[petsc-dev] viewing factored matrices

[Jed Brown]

Barry Smith <bsmith at mcs.anl.gov> writes:

>> Indeed, but I thought we wanted to avoid this because it can lead to
>> options being checked on each iteration
>
>     No, no, and no.  Look in mg.c 
>
>  if (!pc->setupcalled) {
>     for (i=0; i<n; i++) {
>       ierr = KSPSetFromOptions(mglevels[i]->smoothd);CHKERRQ(ierr);

In gamg.c:

  PetscBool      redo_mesh_setup = (PetscBool)(!pc_gamg->reuse_prol);

    if (redo_mesh_setup) {
      /* reset everything */
      ierr = PCReset_MG(pc);CHKERRQ(ierr);
      pc->setupcalled = 0;

The number of levels can change because the strength of connection and
thus thresholding changes.

>    You are correct that currently there are other unprotected calls in
>    fieldsplit.c but I think they can be easily fixed so that the inner
>    SetFromOptions() is called only when setup called is zero. Having
>    non-nested XXXSetFromOptions() has nothing to do with things being
>    check every iteration stuff.

Fair enough, the case above is a different issue and I agree that your
other points are at the very least, pragmatic.
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