[petsc-users] Automatically re-solving after MUMPS error

[Barry Smith]

> On Sep 30, 2015, at 1:06 PM, Matt Landreman <matt.landreman at gmail.com> wrote:
> 
> PETSc developers,
> 
> I tried implementing a system for automatically increasing MUMPS ICNTL(14), along the lines described in this recent thread. If SNESSolve returns ierr .ne. 0 due to MUMPS error -9, I call SNESDestroy, re-initialize SNES, call MatMumpsSetIcntl with a larger value of ICNTL(14), call SNESSolve again, and repeat as needed. The procedure works, but the peak memory required (as measured by the HPC system) is 50%-100% higher if the MUMPS solve has to be repeated compared to when MUMPS works on the 1st try (by starting with a large ICNTL(14)), even though SNESDestroy is called in between the attempts. Are there some PETSc or MUMPS structures which would not be deallocated immediately by SNESDestroy?  If so, how do I deallocate them?

   They should be all destroyed automatically for you. You can use PetscMallocDump() after the SNES is destroyed to verify that all that memory is not properly freed. 

   My guess is that your new malloc() with the bigger workspace cannot "reuse" the space that was previously freed; so to the OS it looks like you are using a lot more space but in terms of physical memory you are not using more.

  Barry

> 
> Thanks,
> Matt Landreman
> 
> 
> On Tue, Sep 15, 2015 at 7:47 AM, David Knezevic <david.knezevic at akselos.com> wrote:
> On Tue, Sep 15, 2015 at 7:29 PM, Matthew Knepley <knepley at gmail.com> wrote:
> On Tue, Sep 15, 2015 at 4:30 AM, David Knezevic <david.knezevic at akselos.com> wrote:
> In some cases, I get MUMPS error -9, i.e.:
> [2]PETSC ERROR: Error reported by MUMPS in numerical factorization phase: INFO(1)=-9, INFO(2)=98927
> 
> This is easily fixed by re-running the executable with -mat_mumps_icntl_14 on the commandline.
> 
> However, I would like to update my code in order to do this automatically, i.e. detect the -9 error and re-run with the appropriate option. Is there a recommended way to do this? It seems to me that I could do this with a PETSc error handler (e.g. PetscPushErrorHandler) in order to call a function that sets the appropriate option and solves again, is that right? Are there any examples that illustrate this type of thing?
> 
> I would not use the error handler. I would just check the ierr return code from the solver. I think you need the
> INFO output, for which you can use MatMumpsGetInfo().
> 
> 
> OK, that sounds good (and much simpler than what I had in mind), thanks for the help!
> 
> David
> 
>