[petsc-users] updating values in a DA Global array

[Mark Cheeseman]

Hi,

I am trying to write a PETSc program in FORTRAN90 where I need to update a
single value in a global distributed array.  I know the global coordinates
of the position that needs to be updated in the global array but I cannot
get the mapping from the local vector correct.  In this case, I am working
on a domain with global dimensions [arraysize(1),arraysize(2),arraysize(3)]
and I want to alter a single point in the global distributed array, uGLOBAL,
at the global position [arraysize(1)/2-1,arraysize(2)-1,3].  I cannot seem
to be able to do this... what am I doing wrong?

...
DA da
Vec uGLOBAL, uLOCAL, tmp
PetscErrorCode ierr
PetscScalar, pointer :: xx
PetscInt rank, source_rank, i,j,k, row

....

call MPI_Comm_rank( PETSC_COMM_WORLD, rank, ierr )
call DACreate3d( PETSC_COMM_WORLD, DA_NONPERIODIC, DA_STENCIL_BOX,       &
                      arraysize(1), arraysize(2), arraysize(3),
PETSC_DECIDE, &
                      PETSC_DECIDE, PETSC_DECIDE, 1, 5,
PETSC_NULL_INTEGER,   &
                      PETSC_NULL_INTEGER, PETSC_NULL_INTEGER, da, ierr)
call DACreateGlobalVector( da, pNOW, ierr )
call DAGetCorners( da, xs, ys, zs, xl, yl, zl, ierr )

    do i = xs,xs+xl-1
        if ( i.eq.arraysize(1)/2-1 ) then
           src_loc(1) = i
           do j = ys,ys+yl-1
              if ( j.eq.arraysize(2)/2-1 ) then
                 src_loc(2) = j
                 do k = zs,zs+zl-1
                    if ( k.eq.3 ) then
                       src_loc(2) = j
                       source_rank = rank
                    endif
                 enddo
              endif
           enddo
        endif
     enddo

call DAGetLocalVector( da, uLOCAL, ierr )
call VecGetArrayF90( uLOCAL, xx, ierr )

if  ( rank.eq.source_rank )  then
     row = 15
     xx(row) = pressure
endif

call VecRestoreArrayF90( uLOCAL, xx, ierr )
call DALocalToGlobal( da, uLOCAL, ADD_VALUES, uGLOBAL, ierr )
call DARestoreLocalVector( da, uLOCAL, ierr )


Any help would be greatly appreciated.  Is there a way to directly access
the global distributed array (uGLOBAL) instead of working through the
intermediate local array (uLOCAL)?  I have tried the approach

call DAVecGetArray( da, uGLOBAL, xx, ierr )
xx = ....
call DAVecRestoreArray( da, uGLOBAL, xx, ierr )

Unfortunately, the compile always fails with the message that the
DAVecRestoreArray function cannot be found.

Thank you,
Mark

-- 
Mark Patrick Cheeseman

Computational Scientist
KSL (KAUST Supercomputing Laboratory)
Building 1, Office #126
King Abdullah University of Science & Technology
Thuwal 23955-6900
Kingdom of Saudi Arabia

EMAIL   : mark.cheeseman at kaust.edu.sa
PHONE : +966   (2) 808 0221 (office)
              +966 (54) 470 1082 (mobile)
SKYPE : mark.patrick.cheeseman
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