[petsc-dev] Use KSPSetUpNorms_Private() in KSPSetFromOptions()

Tue Feb 26 21:54:19 CST 2013

Here's what I get with this simple example (source and makefile also
attached):

#include <petscksp.h>

#undef __FUNCT__
#define __FUNCT__ "main"
int main(int argc,char **args)
{
  KSP            ksp;
  PetscErrorCode ierr;
  PetscInitialize(&argc,&args,(char*)0,(char*)0);
  ierr = KSPCreate(PETSC_COMM_WORLD, &ksp);CHKERRQ(ierr);
  ierr = KSPSetPCSide(ksp, PC_RIGHT);CHKERRQ(ierr);
  ierr = KSPSetFromOptions(ksp);CHKERRQ(ierr);
  ierr = KSPDestroy(&ksp);CHKERRQ(ierr);
  PetscFinalize();
}

Then

[hal3 Tue Feb 26 09:34 PM] ~/petsc/dev/c/src/ksp/ksp/examples/tutorials/tmp
>./ex -ksp_type preonly -ksp_pc_side left
[0]PETSC ERROR: --------------------- Error Message
------------------------------------
[0]PETSC ERROR: No support for this operation for this object type!
[0]PETSC ERROR: KSP preonly does not support RIGHT!
[0]PETSC ERROR:
------------------------------------------------------------------------
[0]PETSC ERROR: Petsc Development HG revision:
55699a42ce9360fb4641931ab7ec242cba302c58  HG Date: Mon Feb 25 22:15:44 2013
-0500
[0]PETSC ERROR: See docs/changes/index.html for recent updates.
[0]PETSC ERROR: See docs/faq.html for hints about trouble shooting.
[0]PETSC ERROR: See docs/index.html for manual pages.
[0]PETSC ERROR:
------------------------------------------------------------------------
[0]PETSC ERROR: ./ex on a arch-gxx-real named hal3 by karpeev Tue Feb 26
21:37:13 2013
[0]PETSC ERROR: Libraries linked from
/home/karpeev/petsc/dev/c/arch-gxx-real/lib
[0]PETSC ERROR: Configure run at Tue Feb 26 17:50:35 2013
[0]PETSC ERROR: Configure options --PETSC_ARCH=arch-gxx-real
--download-f-blas-lapack=1 --download-mpich=1 --with-cc=gcc
--with-clanguage=C++ --with-cxx=g++ --with-dynamic-loading=1
--with-python=1 --with-scalar-type=real --with-shared-libraries=1
[0]PETSC ERROR:
------------------------------------------------------------------------
[0]PETSC ERROR: KSPSetUpNorms_Private() line 385 in
/home/karpeev/petsc/dev/c/src/ksp/ksp/interface/itcreate.c
[0]PETSC ERROR: KSPSetFromOptions() line 409 in
/home/karpeev/petsc/dev/c/src/ksp/ksp/interface/itcl.c
[0]PETSC ERROR: main() line 13 in ex.c
application called MPI_Abort(MPI_COMM_WORLD, 56) - process 0
[unset]: aborting job:
application called MPI_Abort(MPI_COMM_WORLD, 56) - process 0
[hal3 Tue Feb 26 09:37 PM] ~/petsc/dev/c/src/ksp/ksp/examples/tutorials/tmp
>

The problem seems to be this clause in KSPSetUpNorms_Private():

        if (ksp->normtype == KSP_NORM_DEFAULT && i == KSP_NORM_NONE &&
ksp->normsupporttable[i][j] <= 1) {
          continue; /* Skip because we don't want to default to no norms
unless set by the KSP (preonly). */

It is hit because of the code in KSPCreate_PREONLY() you quoted:

  ierr = KSPSetSupportedNorm(ksp,KSP_NORM_NONE,PC_LEFT,2);CHKERRQ(ierr); /*
LEFT/RIGHT is arbitrary, so "support" both */
  ierr = KSPSetSupportedNorm(ksp,KSP_NORM_NONE,PC_RIGHT,1);CHKERRQ(ierr);

The problem is that PC_RIGHT is preferred by KSP_NORM only with priority 1,
which is too weak to overcome
that "continue" clause above.

One way to fix it is to jack up the priority of PC_RIGHT, but I still don't
understand why this combination
of norms and pc sides is being figured out in KSPSetFromOptions() (twice)
with only partial KSP data.
And then again, this time "for real", in KSPSetUp().

Dmitry.

On Wed, Feb 27, 2013 at 2:52 AM, Barry Smith <bsmith at mcs.anl.gov> wrote:

>
> On Feb 26, 2013, at 4:44 PM, Dmitry Karpeev <karpeev at mcs.anl.gov> wrote:
>
> > These calls compute default values for normtype and pcside based on
> partial KSP options,
> > which can cause an unwarranted error to be thrown.
> > For example, in code there may be
> >
> > KSPSetPCSide(ksp, PC_RIGHT); /* hardwired default, e.g., in Moose. */
> >
> > Now, when I'm using command-line arguments
> > -ksp_type preonly
> > an error is thrown, since KSPPREONLY doesn't work with PC_RIGHT.
>
>   Huh?
>
> EXTERN_C_BEGIN
> #undef __FUNCT__
> #define __FUNCT__ "KSPCreate_PREONLY"
> PetscErrorCode  KSPCreate_PREONLY(KSP ksp)
> {
>   PetscErrorCode ierr;
>
>   PetscFunctionBegin;
>   ierr = KSPSetSupportedNorm(ksp,KSP_NORM_NONE,PC_LEFT,2);CHKERRQ(ierr);
> /* LEFT/RIGHT is arbitrary, so "support" both */
>   ierr = KSPSetSupportedNorm(ksp,KSP_NORM_NONE,PC_RIGHT,1);CHKERRQ(ierr);
>
> Is it because MOOSE also hardwires the norm type and preonly doesn't
> support it? What is the full and complete error message.
>
> > Fine, I try
> > -ksp_type preonly -ksp_pc_side left
> > but still get the same error, since KSPSetUpNorms_Private() is called
> after KSP type has been set to KSPPREONLY,
> > but BEFORE there was a chance to set the PC side!
> >
> > Is there any reason to keep these calls to KSPSetUpNorms_Private() in
> KSPSetFromOptions()?
>
>    I think they are there so that users can overwrite them in the rest of
> KSPSetFromOptions(). If you move them to KSPSetUp() then the user cannot
> reset them.
>
>    Barry
>
>
> > KSPSetUpNorms_Private() will be just about the first thing called in
> KSPSetUp() and will compute the appropriate normtype and pcside,
> > but now based on complete KSP options.
> >
> > Not to mention that calling XXXSetUp_YYY() XXXSetFromOptions() seems
> generally contrary to PETSc's design
> > philosophy.
> >
> > Dmitry.
> >
> >
>
>
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