The missing third argument to PCApply means that you haven't allocated the 
vector work?


> On Sep 9, 2016, at 3:34 PM, Manuel Valera <[email protected]> wrote:
> 
> Hello everyone,
> 
> I'm having an error with my program that i cannot understand, the weird part 
> is that the same implementation in my main model does not show errors and 
> they are virtually identical.
> 
> The problematic part of the code is:
> 
> 
>   call KSPCreate(PETSC_COMM_WORLD,ksp,ierr)
>   call KSPSetOperators(ksp,Ap,Ap,ierr)   
>   call KSPGetPC(ksp,pc,ierr)
>   tol = 1.e-5
>   call 
> KSPSetTolerances(ksp,tol,PETSC_DEFAULT_REAL,PETSC_DEFAULT_REAL,PETSC_DEFAULT_INTEGER,ierr)
> 
>   call PCGetOperators(pc,PETSC_NULL_OBJECT,pmat,ierr)
>   call PCCreate(PETSC_COMM_WORLD,mg,ierr)
>   call PCSetType(mg,PCJACOBI,ierr)
>   call PCSetOperators(mg,pmat,pmat,ierr)
>   call PCSetUp(mg,ierr)
> 
>   call PCApply(mg,xp,work,ierr)
> 
> 
> And the errors i get are:
> 
> [0]PETSC ERROR: --------------------- Error Message 
> --------------------------------------------------------------
> [0]PETSC ERROR: Null argument, when expecting valid pointer
> [0]PETSC ERROR: Null Object: Parameter # 3
> [0]PETSC ERROR: See http://www.mcs.anl.gov/petsc/documentation/faq.html for 
> trouble shooting.
> [0]PETSC ERROR: Petsc Release Version 3.7.3, Jul, 24, 2016 
> [0]PETSC ERROR: ./solvelinearmgPETSc                                          
>                                                                               
>                                                                               
>                                                  on a arch-linux2-c-debug 
> named valera-HP-xw4600-Workstation by valera Fri Sep  9 12:46:02 2016
> [0]PETSC ERROR: Configure options --with-cc=gcc --with-cxx=g++ 
> --with-fc=gfortran --download-fblaslapack=1 --download-mpich=1 
> --download-ml=1
> [0]PETSC ERROR: #1 PCApply() line 467 in 
> /home/valera/sergcemv4/bitbucket/serucoamv4/petsc-3.7.3/src/ksp/pc/interface/precon.c
> [0]PETSC ERROR: --------------------- Error Message 
> --------------------------------------------------------------
> [0]PETSC ERROR: Null argument, when expecting valid pointer
> [0]PETSC ERROR: Null Object: Parameter # 3
> [0]PETSC ERROR: See http://www.mcs.anl.gov/petsc/documentation/faq.html for 
> trouble shooting.
> [0]PETSC ERROR: Petsc Release Version 3.7.3, Jul, 24, 2016 
> [0]PETSC ERROR: ./solvelinearmgPETSc                                          
>                                            
> 
> 
> As i said before, the exact same code in a bigger model does not print 
> errors. I'm trying to solve this before moving into multigrid implementation 
> in my prototype, 
> 
> Thanks for your time,
> 
> 
> 
> On Wed, Sep 7, 2016 at 8:27 PM, Barry Smith <[email protected]> wrote:
> 
> > On Sep 7, 2016, at 10:24 PM, Manuel Valera <[email protected]> wrote:
> >
> > Thank you I will try this. What would be the call if I wanted to use other 
> > Multigrid option?
> 
>    There really isn't any other choices.
> 
> > Don't worry this is a standalone prototype, it should be fine on the main 
> > model. Anyway, any hints would be appreciated. Thanks a lot for your time.
> >
> >
> > On Sep 7, 2016 8:22 PM, "Barry Smith" <[email protected]> wrote:
> >
> >   Sorry, this was due to our bug, the fortran function for PCGAMGSetType() 
> > was wrong. I have fixed this in the maint and master branch of PETSc in the 
> > git repository. But you can simply remove the call to PCGAMGSetType() from 
> > your code since what you are setting is the default type.
> >
> >   BTW: there are other problems with your code after that call that you 
> > will have to work through.
> >
> >   Barry
> >
> > > On Sep 7, 2016, at 8:46 PM, Manuel Valera <[email protected]> wrote:
> > >
> > >
> > > ---------- Forwarded message ----------
> > > From: Manuel Valera <[email protected]>
> > > Date: Wed, Sep 7, 2016 at 6:40 PM
> > > Subject: Re: [petsc-users] Sorted CSR Matrix and Multigrid PC.
> > > To:
> > > Cc: PETSc users list <[email protected]>
> > >
> > >
> > > Hello,
> > >
> > > I was able to sort the data but the PCGAMG does not seem  to be working.
> > >
> > > I reconfigured everything from scratch as suggested and updated to the 
> > > latest PETSc version, same results,
> > >
> > > I get the following error:
> > >
> > > [0]PETSC ERROR: Caught signal number 11 SEGV: Segmentation Violation, 
> > > probably memory access out of range
> > > [...]
> > > [0]PETSC ERROR: ---------------------  Stack Frames 
> > > ------------------------------------
> > > [0]PETSC ERROR: Note: The EXACT line numbers in the stack are not 
> > > available,
> > > [0]PETSC ERROR:       INSTEAD the line number of the start of the function
> > > [0]PETSC ERROR:       is given.
> > > [0]PETSC ERROR: [0] PetscStrcmp line 524 
> > > /home/valera/sergcemv4/bitbucket/serucoamv4/petsc-3.7.3/src/sys/utils/str.c
> > > [0]PETSC ERROR: [0] PetscFunctionListFind_Private line 352 
> > > /home/valera/sergcemv4/bitbucket/serucoamv4/petsc-3.7.3/src/sys/dll/reg.c
> > > [0]PETSC ERROR: [0] PCGAMGSetType_GAMG line 1157 
> > > /home/valera/sergcemv4/bitbucket/serucoamv4/petsc-3.7.3/src/ksp/pc/impls/gamg/gamg.c
> > > [0]PETSC ERROR: [0] PCGAMGSetType line 1102 
> > > /home/valera/sergcemv4/bitbucket/serucoamv4/petsc-3.7.3/src/ksp/pc/impls/gamg/gamg.c
> > > [0]PETSC ERROR: --------------------- Error Message 
> > > --------------------------------------------------------------
> > > ....
> > >
> > > You can find the working program attached, sorry for the large files and 
> > > messy makefile,
> > >
> > > Many thanks,
> > >
> > > Manuel Valera.
> > >
> > >
> > > ​
> > >  MGpetscSolver.tar.gz
> > > ​
> > >
> >
> 
> 

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