[petsc-users] SNESSetOptionsPrefix usage

[Smith, Barry F.]

  Works for me with PETSc 12, what version of PETSc are you using?


      program main
#include <petsc/finclude/petsc.h>
      use petsc
      implicit none


! - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

      PetscErrorCode  ierr

      SNES snes1
 

      call PetscInitialize(PETSC_NULL_CHARACTER,ierr)
      if (ierr .ne. 0) then
        print*,'Unable to initialize PETSc'
        stop
      endif

      call SNESCreate(MPI_COMM_SELF,snes1,ierr)
      call SNESSetOptionsPrefix(snes1,'green_',ierr)
      call SNESSetFromOptions(snes1,ierr)


      call SNESDestroy(snes1,ierr)
 
      call PetscFinalize(ierr)
      end

$ ./ex1f -green_snes_monitor 
~/Src/petsc/src/snes/examples/tutorials (oanam/sem-pde-optimization *=) 
$ ./ex1f -green_snes_monitor -options_left
#PETSc Option Table entries:
-check_pointer_intensity 0
-green_snes_monitor
-malloc_dump
-options_left
#End of PETSc Option Table entries
There are no unused options.
~/Src/petsc/src/snes/examples/tutorials (oanam/sem-pde-optimization *=) 



> On Jan 15, 2020, at 4:03 AM, Timothée Nicolas <timothee.nicolas at gmail.com> wrote:
> 
> Dear PETSc users,
> 
> I am confused by the usage of SNESSetOptionsPrefix. I understand this is required if you have for example different SNES in your program and want to set different options for them.
> So for my second snes I wrote 
> 
> call SNESCreate(MPI_COMM_SELF,snes,ierr)
> call SNESSetOptionsPrefix(snes,'green_',ierr)
> call SNESSetFromOptions(snes,ierr)
> 
> etc.
> 
> Then when launching the program I wanted to monitor that snes so I launched it with the option -green_snes_monitor instead of -snes_monitor. But I keep getting the message
> 
> WARNING! There are options you set that were not used!
> WARNING! could be spelling mistake, etc!
> Option left: name:-green_snes_monitor (no value)
> 
> What do I miss here?
> 
> Best regards
> 
> Timothée NICOLAS