1: !
  2: !  Description: Creates an index set based on a set of integers. Views that index set
  3: !  and then destroys it.
  4: !
  5: !/*T
  6: !    Concepts: index sets^manipulating a general index set;
  7: !T*/
  8: !
  9: !
 10:       program main
 11:  #include <petsc/finclude/petscis.h>
 12:       use petscis
 13:       implicit none

 15:       PetscErrorCode ierr
 16:       PetscInt indices(5),n,index1,index5
 17:       PetscMPIInt rank
 18:       PetscOffset ix
 19:       IS          is

 21:       call PetscInitialize(PETSC_NULL_CHARACTER,ierr)
 22:       if (ierr .ne. 0) then
 23:         print*,'Unable to initialize PETSc'
 24:         stop
 25:       endif
 26:       call MPI_Comm_rank(PETSC_COMM_WORLD,rank,ierr)

 28: !  Create an index set with 5 entries. Each processor creates
 29: !  its own index set with its own list of integers.

 31:       indices(1) = rank + 1
 32:       indices(2) = rank + 2
 33:       indices(3) = rank + 3
 34:       indices(4) = rank + 4
 35:       indices(5) = rank + 5

 37: !     if using 64bit integers cannot pass 5 into routine expecting an integer*8
 38:       n = 5
 39:       call ISCreateGeneral(PETSC_COMM_SELF,n,indices,PETSC_COPY_VALUES,       &
 40:      &                     is,ierr)

 42: !  Print the index set to stdout

 44:       call ISView(is,PETSC_VIEWER_STDOUT_SELF,ierr)

 46: !  Get the number of indices in the set

 48:       call ISGetLocalSize(is,n,ierr)

 50: !   Get the indices in the index set

 52:       call ISGetIndices(is,indices,ix,ierr)

 54: !   Now any code that needs access to the list of integers
 55: !   has access to it here

 57: !
 58: !      Bug in IRIX64-F90 libraries - write/format cannot handle integer(integer*8 + integer)
 59: !

 61:       index1 = indices(ix+1)
 62:       index5 = indices(ix+5)
 63:       write(6,100) rank,index1,index5
 64:  100  format('[',i5,'] First index = ',i5,' fifth index = ',i5)

 66: !   Once we no longer need access to the indices they should
 67: !   returned to the system

 69:       call ISRestoreIndices(is,indices,ix,ierr)

 71: !   All PETSc objects should be destroyed once they are
 72: !   no longer needed

 74:       call ISDestroy(is,ierr)
 75:       call PetscFinalize(ierr)
 76:       end