[petsc-users] How to set up -mat_mumps_icntl13 1 in the code?

[Giacomo Mulas]

On Mon, 14 May 2012, Matthew Knepley wrote:

> The problems below are exactly why we do not advocate this strategy.
> However, you
> can get this effectusing http://www.mcs.anl.gov/petsc/petsc-dev/docs/manualpages/Sys/PetscOpti
> onsSetValue.html

Thanks Matt!

Hmm, this would be more or less the same as adding the options to argc and
argv before initialising slepc and petsc, I gather. Functional, even if not
quite as clean as I would have liked. My idea was to set some working
default in the code, but still honor command line options if different, 
whereas what you suggest overrides any conflicting command line options. 
Indeed, in my code I call EPSSetFromOptions() _after_ my explicit function
calls, to make sure that command line options override my defaults (at
least, that's my intended logic...).

Maybe I should first check for appropriate command line options, and then
set them in the code _only if_ none were given on the command line?
What about:
 	  PetscInt ival;
 	  PetscBool isset;
 	  ierr = PetscOptionsGetInt(PETSC_NULL, "-mat_mumps_icntl_13",
 	  &ival,
 				    &isset);CHKERRQ(ierr);
 	  if (isset==PETSC_FALSE) {
 	    ierr = PetscOptionsSetValue("-mat_mumps_icntl_13","1");
 	    CHKERRQ(ierr);
 	  }

Does it look sensible?

Also, could you please specify a bit more what strategy you do not advocate,
and for what problems? Do you mean setting up options by direct function
calls, as opposed to setting them via PetscOptionsSetValue() ?
Or do you mean it is deprecated to set options in the code in any way, be it
via direct function calls or via PetscOptionsSetValue() ?

And the problems you are referring to are essentially the runtime error I
get, i.e. calling functions in the wrong order? Or something else?

Finally, if I call EPSGetST(), should I then call STDestroy() on the ST I
obtained, or will it be done by EPSDestroy()? And the same question iterates
for the KSP I obtained via STGetKSP(), and the PC I obtained via KSPGetPC().

Thanks, bye
Giacomo

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Giacomo Mulas <gmulas at oa-cagliari.inaf.it>
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