Actual source code: ex3f.F90

  1: !
  2: !
  3: !  Description: Displays a vector visually.
  4: !
  5: ! -----------------------------------------------------------------------

  7: program main
  8: #include <petsc/finclude/petscvec.h>
  9:   use petscvec
 10:   implicit none

 12: ! - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 13: !                 Beginning of program
 14: ! - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

 16:   Vec x
 17:   PetscViewer viewer
 18:   PetscScalar v
 19:   PetscInt :: i, istart, iend
 20:   PetscInt, parameter :: ione = 1, n = 50
 21:   PetscErrorCode ierr
 22:   PetscBool flg
 23:   integer4 xl, yl, w, h

 25:   PetscCallA(PetscInitialize(ierr))
 26:   PetscCallA(PetscOptionsGetInt(PETSC_NULL_OPTIONS, PETSC_NULL_CHARACTER, '-n', n, flg, ierr))

 28: !  Create a vector, specifying only its global dimension.
 29: !  When using VecCreate(), VecSetSizes() and VecSetFromOptions(),
 30: !  the vector format (currently parallel
 31: !  or sequential) is determined at runtime.  Also, the parallel
 32: !  partitioning of the vector is determined by PETSc at runtime.
 33:   PetscCallA(VecCreate(PETSC_COMM_WORLD, x, ierr))
 34:   PetscCallA(VecSetSizes(x, PETSC_DECIDE, n, ierr))
 35:   PetscCallA(VecSetFromOptions(x, ierr))

 37: !  Currently, all PETSc parallel vectors are partitioned by
 38: !  contiguous chunks of rows across the processors.  Determine
 39: !  which vector are locally owned.
 40:   PetscCallA(VecGetOwnershipRange(x, istart, iend, ierr))

 42: !  Set the vector elements.
 43: !   - Always specify global locations of vector entries.
 44: !   - Each processor needs to insert only elements that it owns locally.
 45:   do 100 i = istart, iend - 1
 46:     v = 1.0*real(i)
 47:     PetscCallA(VecSetValues(x, ione, [i], [v], INSERT_VALUES, ierr))
 48: 100 continue

 50: !  Assemble vector, using the 2-step process:
 51: !    VecAssemblyBegin(), VecAssemblyEnd()
 52: !  Computations can be done while messages are in transition
 53: !  by placing code between these two statements.
 54:     PetscCallA(VecAssemblyBegin(x, ierr))
 55:     PetscCallA(VecAssemblyEnd(x, ierr))

 57: !  Open an X-window viewer.  Note that we specify the same communicator
 58: !  for the viewer as we used for the distributed vector (PETSC_COMM_WORLD).
 59: !    - Helpful runtime option:
 60: !         -draw_pause <pause> : sets time (in seconds) that the
 61: !               program pauses after PetscDrawPause() has been called
 62: !              (0 is default, -1 implies until user input).

 64:     xl = 0
 65:     yl = 0
 66:     w = 300
 67:     h = 300
 68:     PetscCallA(PetscViewerDrawOpen(PETSC_COMM_WORLD, PETSC_NULL_CHARACTER, PETSC_NULL_CHARACTER, xl, yl, w, h, viewer, ierr))

 70: !  View the vector
 71:     PetscCallA(VecView(x, viewer, ierr))

 73: !  Free work space.  All PETSc objects should be destroyed when they
 74: !  are no longer needed.

 76:     PetscCallA(PetscViewerDestroy(viewer, ierr))
 77:     PetscCallA(VecDestroy(x, ierr))

 79:     PetscCallA(PetscFinalize(ierr))
 80:   end

 82: !/*TEST
 83: !
 84: !     test:
 85: !       nsize: 2
 86: !       output_file: output/empty.out
 87: !
 88: !TEST*/