[petsc-users] Fortran 77 VecGetArray problems

[Valerio Grazioso]

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 ------------------------------
>> 
>> 
>