[petsc-users] Fortran 77 VecGetArray problems

[Satish Balay]

Great!

BTW: since most compilers (including gfortran) now support F90 - its
best to use VecGetArrayF90 - instead of VecGetArray() [eventhough the
rest of the code is F77]

Satish

On Sat, 22 Nov 2014, Valerio Grazioso wrote:

> Ehi Barry,
> thanks a lot… that was the problem: I had the -fbounds-check flag of gfortran in my Makefile…removing it everything is ok !
> (Of course …it was in the manual…  !! :)   )
> 
> Valerio
> 
> 
> 
> 
> On 21/nov/2014, at 14:18, Barry Smith <bsmith at mcs.anl.gov> wrote:
> 
> > 
> >> On Nov 20, 2014, at 9:19 PM, Valerio Grazioso <graziosov at libero.it> wrote:
> >> 
> >> Dear Petsc Users,
> >> I’m trying to write a simple parallel linear solver (A*x=q) in fortran 77 with Petsc.
> >> I managed to Setup a MPIAIJ matrix A  and a VecMPI qvec
> >> then the KSP and the solution.
> >> Everything seems fine (I’ve checked both A and q with MatView and VecView) but I’m having problems getting the solution in a “normal” local double precision fortran vector.
> >> 
> >> To be more than sure I’ve tried to repeat the necessary steps in order to achieve this result on qvec :
> >> 
> >> After creating and calling a VecScatter in order to bring a sequential version on all the processors (as described in 
> >> http://www.mcs.anl.gov/petsc/petsc-as/documentation/faq.html#mpi-vec-to-mpi-vec)
> >> I’ve tried to use VecGetValue as described in the User manual in the Fortran users chapter (pag. 147-148)
> >> It seems to fail in both the local xx_v vector (that has wrong values) and in calculating the i_x index offset that has a very large negative value
> >> that, when it is used, generates an obvious “Aut of bound” error.
> > 
> >   It is completely possible that i_x is a very large negative value, in fact it usually is.
> > 
> >   From the users manual:  Note: If using VecGetArray(), MatDenseGetArray(), or ISGetIndices(), from Fortran, the user must not compile the Fortran code with options to check for “array entries out of bounds” (e.g., on the IBM RS/6000 this is done with the -C compiler option, so never use the -C option with this).
> > 
> >  My guess is that your Fortran compiler is checking for array out of bounds and (of course) finding them since xx_v() is declared as xx_v(1). You need to turn of this array bounds checking when compiling. Or you can use VecGetArrayF90().
> > 
> >   Barry
> > 
> > 
> > 
> >> I’ve tried to use VecGetValue also on qvec directly : same result!
> >> 
> >> There must be something wrong that I’m doing.
> >> Can anybody point me in the right direction?
> >> Thanks 
> >> 
> >> Regards
> >> Valerio Grazioso
> >> 
> >> 
> >> Here it is the relevant code:
> >> 
> >> 
> >> 
> >> #define xx_a(ib)  xx_v(i_x + (ib))
> >> 
> >> …………………..  
> >> 
> >>     Vec         xSEQ
> >>     PetscScalar xx_v(1)
> >>     PetscOffset i_x
> >> 
> >>     ……………………..
> >>    ………………..
> >> 
> >> 
> >>     write(6,'(a,i2,a)'),"Processor  ",mpi_rank,": petsc_solve ---> VecCreate"
> >>     call VecCreate(comm,qvec,ierr); CHKERRQ(ierr)     
> >> 
> >>     write(6,'(a,i2,a)'),"Processor  ",mpi_rank,": petsc_solve ---> VecSetSizes"
> >>     call VecSetSizes(qvec,PETSC_DECIDE,NCELL,ierr); CHKERRQ(ierr)
> >> 
> >>     write(6,'(a,i2,a)'),"Processor  ",mpi_rank,": petsc_solve ---> VecSetFromOptions"
> >>     call VecSetFromOptions(qvec,ierr); CHKERRQ(ierr)
> >> 
> >>     write(6,'(a,i2,a)'),"Processor  ",mpi_rank,": petsc_solve ---> VecDuplicate"
> >>     call VecDuplicate(qvec,xvec,ierr); CHKERRQ(ierr)
> >> 
> >>     write(6,'(a,i2,a)'),"Processor  ",mpi_rank,": petsc_solve ---> VecGetOwnershipRange"
> >>     call VecGetOwnershipRange(qvec,Istart,Iend,ierr); CHKERRQ(ierr)
> >> 
> >>     write(6,'(a,i2,a,2i8)'),"Processor  ",mpi_rank,": petsc_solve ---> Istart,Iend (Vet)=", Istart,Iend
> >> 
> >>     do Iproc = 0,(mpi_size-1)
> >>       if (Iproc == mpi_rank) then 
> >>         do I= (Istart+1), (Iend)
> >> C            write(6,'(a,i2,a,2i8)'),"Processor  ",mpi_rank,": petsc_solve ---> MatSetValues",I,I
> >>           call VecSetValues(qvec,1,I-1,SU(I),INSERT_VALUES,ierr); CHKERRQ(ierr)
> >>           call VecSetValues(xvec,1,I-1,0.E0,INSERT_VALUES,ierr); CHKERRQ(ierr)
> >>         enddo
> >>       endif
> >>     enddo
> >> 
> >>     write(6,'(a,i2,a)'),"Processor  ",mpi_rank,": petsc_solve ---> VecAssemblyBegin"
> >>     call VecAssemblyBegin(qvec,ierr); CHKERRQ(ierr)
> >>     call VecAssemblyEnd(qvec,ierr); CHKERRQ(ierr) 
> >>     call VecAssemblyBegin(xvec,ierr); CHKERRQ(ierr) 
> >>     call VecAssemblyEnd(xvec,ierr); CHKERRQ(ierr) 
> >>     write(6,'(a,i2,a)'),"Processor  ",mpi_rank,": petsc_solve ---> VecAssemblyEnd"
> >> 
> >> C ---------------------------------  DEBUG -------------------------------------
> >>     if (1 == 1) then
> >> 
> >>        call VecScatterCreateToAll(qvec,ctx,xSEQ,ierr); CHKERRQ(ierr)
> >>        call VecScatterBegin(ctx,qvec,xSEQ,INSERT_VALUES,SCATTER_FORWARD,ierr)
> >>        CHKERRQ(ierr)
> >>        call VecScatterEnd(ctx,qvec,xSEQ,INSERT_VALUES,SCATTER_FORWARD,ierr)
> >>        CHKERRQ(ierr)
> >>        call VecScatterDestroy(ctx,ierr); CHKERRQ(ierr)
> >> 
> >> C         call PetscViewerCreate(comm, view, ierr); CHKERRQ(ierr)
> >> C         call PetscViewerSetType(view, PETSCVIEWERASCII, ierr); CHKERRQ(ierr)
> >> C         call PetscViewerSetFormat(view, PETSC_VIEWER_ASCII_INDEX, ierr)
> >> C         CHKERRQ(ierr)
> >> C         call PetscViewerFileSetName(view, 'qvec.m', ierr)
> >> C         call VecView(xSEQ, view, ierr); CHKERRQ(ierr)
> >> C         call PetscViewerDestroy(view, ierr); CHKERRQ(ierr)
> >> 
> >>        call VecGetArray(xSEQ,xx_v,i_x,ierr); CHKERRQ(ierr)
> >> 
> >>           write(6, *) (xx_a(I), I=1,NCELL)
> >>           write(6,'(a,i20)')"i_x = ", i_x 
> >> 
> >> 
> >>        call VecRestoreArray(xSEQ,xx_v,i_x,ierr); CHKERRQ(ierr)
> >> 
> >>        call PetscFinalize(ierr); CHKERRQ(ierr)
> >>        STOP
> >>     endif
> >> C ---------------------------------- END DEBUG ------------------------------
> >> 
> >> 
> > 
> 
>