Actual source code: ex12f.F90

  1: program main

  3: #include <petsc/finclude/petscvec.h>

  5: use petscvec
  6: implicit none

  8:   PetscErrorCode ierr
  9:   Vec   v,s
 10:   PetscInt,parameter ::      n   = 20
 11:   PetscScalar,parameter ::   sone = 1.0
 12:   PetscBool :: flg
 13:   PetscInt,parameter :: zero = 0, one = 1, two = 2

 15:  call PetscInitialize(PETSC_NULL_CHARACTER,ierr)
 16:   if (ierr /= 0) then
 17:    print*,'PetscInitialize failed'
 18:    stop
 19:   endif

 21:   call PetscOptionsGetInt(PETSC_NULL_OPTIONS,PETSC_NULL_CHARACTER,"-n",n,flg,ierr);CHKERRA(ierr)

 23:   ! Create multi-component vector with 2 components
 24:   call VecCreate(PETSC_COMM_WORLD,v,ierr);CHKERRA(ierr)
 25:   call VecSetSizes(v,PETSC_DECIDE,n,ierr);CHKERRA(ierr)
 26:   call VecSetBlockSize(v,two,ierr);CHKERRA(ierr)
 27:   call VecSetFromOptions(v,ierr);CHKERRA(ierr)

 29:   ! Create single-component vector
 30:   call VecCreate(PETSC_COMM_WORLD,s,ierr);CHKERRA(ierr)
 31:   call VecSetSizes(s,PETSC_DECIDE,n/2,ierr);CHKERRA(ierr)
 32:   call VecSetFromOptions(s,ierr);CHKERRA(ierr)

 34:   !Set the vectors to entries to a constant value.
 35:   call VecSet(v,sone,ierr);CHKERRA(ierr)

 37:   !Get the first component from the multi-component vector to the single vector
 38:   call VecStrideGather(v,zero,s,INSERT_VALUES,ierr);CHKERRA(ierr)

 40:   call VecView(s,PETSC_VIEWER_STDOUT_WORLD,ierr);CHKERRA(ierr)

 42:   !Put the values back into the second component
 43:   call VecStrideScatter(s,one,v,ADD_VALUES,ierr);CHKERRA(ierr)

 45:   call VecView(v,PETSC_VIEWER_STDOUT_WORLD,ierr);CHKERRA(ierr)

 47:   ! Free work space.All PETSc objects should be destroyed when they are no longer needed.
 48:   call VecDestroy(v,ierr);CHKERRA(ierr)
 49:   call VecDestroy(s,ierr);CHKERRA(ierr)
 50:   call PetscFinalize(ierr);CHKERRA(ierr)

 52:   end program

 54: !/*TEST
 55: !
 56: !     test:
 57: !       nsize: 2
 58: !       output_file: output/ex12_1.out
 59: !
 60: !TEST*/