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:   PetscCallA(PetscInitialize(ierr))

 17:   PetscCallA(PetscOptionsGetInt(PETSC_NULL_OPTIONS,PETSC_NULL_CHARACTER,"-n",n,flg,ierr))

 19:   ! Create multi-component vector with 2 components
 20:   PetscCallA(VecCreate(PETSC_COMM_WORLD,v,ierr))
 21:   PetscCallA(VecSetSizes(v,PETSC_DECIDE,n,ierr))
 22:   PetscCallA(VecSetBlockSize(v,two,ierr))
 23:   PetscCallA(VecSetFromOptions(v,ierr))

 25:   ! Create single-component vector
 26:   PetscCallA(VecCreate(PETSC_COMM_WORLD,s,ierr))
 27:   PetscCallA(VecSetSizes(s,PETSC_DECIDE,n/2,ierr))
 28:   PetscCallA(VecSetFromOptions(s,ierr))

 30:   !Set the vectors to entries to a constant value.
 31:   PetscCallA(VecSet(v,sone,ierr))

 33:   !Get the first component from the multi-component vector to the single vector
 34:   PetscCallA(VecStrideGather(v,zero,s,INSERT_VALUES,ierr))

 36:   PetscCallA(VecView(s,PETSC_VIEWER_STDOUT_WORLD,ierr))

 38:   !Put the values back into the second component
 39:   PetscCallA(VecStrideScatter(s,one,v,ADD_VALUES,ierr))

 41:   PetscCallA(VecView(v,PETSC_VIEWER_STDOUT_WORLD,ierr))

 43:   ! Free work space.All PETSc objects should be destroyed when they are no longer needed.
 44:   PetscCallA(VecDestroy(v,ierr))
 45:   PetscCallA(VecDestroy(s,ierr))
 46:   PetscCallA(PetscFinalize(ierr))

 48:   end program

 50: !/*TEST
 51: !
 52: !     test:
 53: !       nsize: 2
 54: !       output_file: output/ex12_1.out
 55: !
 56: !TEST*/