1: !
  2: !     Description: Creates an index set based on a stride. Views that
  3: !     index set and then destroys it.
  4: !
  5: !
  6: !     Include petscis.h so we can use PETSc IS objects.
  7: !
  8:       program main
  9: #include <petsc/finclude/petscis.h>
 10:       use petscis
 11:       implicit none

 13:       PetscErrorCode ierr
 14:       PetscInt    i,n,first,step,val
 15:       IS          set
 16:       PetscInt, pointer :: index(:)

 18:       PetscCallA(PetscInitialize(ierr))
 19:       n     = 10
 20:       first = 3
 21:       step  = 2

 23: !     Create stride index set, starting at 3 with a stride of 2 Note
 24: !     each processor is generating its own index set (in this case they
 25: !     are all identical)

 27:       PetscCallA(ISCreateStride(PETSC_COMM_SELF,n,first,step,set,ierr))
 28:       PetscCallA(ISView(set,PETSC_VIEWER_STDOUT_SELF,ierr))

 30: !     Extract the indices values from the set. Demonstrates how a Fortran
 31: !     code can directly access the array storing a PETSc index set with
 32: !     ISGetIndices().

 34:       PetscCallA(ISGetIndices(set,index,ierr))
 35:       write(6,20)
 36: !     Bug in IRIX64 f90 compiler - write cannot handle
 37: !     integer(integer*8) correctly
 38:       do 10 i=1,n
 39:          val = index(i)
 40:          write(6,30) val
 41:  10   continue
 42:  20   format('Printing indices directly')
 43:  30   format(i3)
 44:       PetscCallA(ISRestoreIndices(set,index,ierr))

 46: !     Determine information on stride

 48:       PetscCallA(ISStrideGetInfo(set,first,step,ierr))
 49:       if (first .ne. 3 .or. step .ne. 2) then
 50:         print*,'Stride info not correct!'
 51:       endif

 53:       PetscCallA(ISDestroy(set,ierr))
 54:       PetscCallA(PetscFinalize(ierr))
 55:       end

 57: !/*TEST
 58: !
 59: !   test:
 60: !
 61: !TEST*/