2: !    Description: A star forest is a simple tree with one root and zero or more leaves.
  3: !    Many common communication patterns can be expressed as updates of rootdata using leafdata and vice-versa.
  4: !     This example creates a star forest, communicates values using the graph  views the graph, then destroys it.
  5: !
  6: !     This is a copy of ex1.c but currently only tests the broadcast operation

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

 13:       PetscErrorCode                ierr
 14:       PetscInt                      i,nroots,nrootsalloc,nleaves,nleavesalloc,mine(6),stride
 15:       type(PetscSFNode)             remote(6)
 16:       PetscMPIInt                   rank,size
 17:       PetscSF                       sf
 18:       PetscInt                      rootdata(6),leafdata(6)

 20: ! used with PetscSFGetGraph()
 21:       type(PetscSFNode), pointer :: gremote(:)
 22:       PetscInt, pointer ::          gmine(:)
 23:       PetscInt                      gnroots,gnleaves;

 25:       call PetscInitialize(PETSC_NULL_CHARACTER,ierr)
 26:       if (ierr .ne. 0) then
 27:         print*,'Unable to initialize PETSc'
 28:         stop
 29:       endif
 30:       stride = 2
 31:       call MPI_Comm_rank(PETSC_COMM_WORLD,rank,ierr);CHKERRA(ierr);
 32:       call MPI_Comm_size(PETSC_COMM_WORLD,size,ierr);CHKERRA(ierr);

 34:       if (rank == 0) then
 35:          nroots = 3
 36:       else
 37:          nroots = 2
 38:       endif
 39:       nrootsalloc  = nroots * stride;
 40:       if (rank > 0) then
 41:          nleaves = 3
 42:       else
 43:          nleaves = 2
 44:       endif
 45:       nleavesalloc = nleaves * stride
 46:       if (stride > 1) then
 47:          do i=1,nleaves
 48:             mine(i) = stride * (i-1)
 49:          enddo
 50:       endif

 52: ! Left periodic neighbor
 53:       remote(1)%rank  = modulo(rank+size-1,size)
 54:       remote(1)%index = 1 * stride
 55: ! Right periodic neighbor
 56:       remote(2)%rank  = modulo(rank+1,size)
 57:       remote(2)%index = 0 * stride
 58:       if (rank > 0) then !               All processes reference rank 0, index
 59:          remote(3)%rank  = 0
 60:          remote(3)%index = 2 * stride
 61:       endif

 63: !  Create a star forest for communication
 64:       call PetscSFCreate(PETSC_COMM_WORLD,sf,ierr);CHKERRA(ierr);
 65:       call PetscSFSetFromOptions(sf,ierr);CHKERRA(ierr);
 66:       call PetscSFSetGraph(sf,nrootsalloc,nleaves,mine,PETSC_COPY_VALUES,remote,PETSC_COPY_VALUES,ierr);CHKERRA(ierr);
 67:       call PetscSFSetUp(sf,ierr);CHKERRA(ierr);

 69: !   View graph, mostly useful for debugging purposes.
 70:       call PetscViewerPushFormat(PETSC_VIEWER_STDOUT_WORLD,PETSC_VIEWER_ASCII_INFO_DETAIL,ierr);CHKERRA(ierr);
 71:       call PetscSFView(sf,PETSC_VIEWER_STDOUT_WORLD,ierr);CHKERRA(ierr);
 72:       call PetscViewerPopFormat(PETSC_VIEWER_STDOUT_WORLD,ierr);CHKERRA(ierr);

 74: !   Allocate space for send and recieve buffers. This example communicates PetscInt, but other types, including
 75: !     * user-defined structures, could also be used.
 76: !     Set rootdata buffer to be broadcast
 77:       do i=1,nrootsalloc
 78:          rootdata(i) = -1
 79:       enddo
 80:       do i=1,nroots
 81:          rootdata(1 + (i-1)*stride) = 100*(rank+1) + i - 1
 82:       enddo

 84: !     Initialize local buffer, these values are never used.
 85:       do i=1,nleavesalloc
 86:          leafdata(i) = -1
 87:       enddo

 89: !     Broadcast entries from rootdata to leafdata. Computation or other communication can be performed between the begin and end calls.
 90:       call PetscSFBcastBegin(sf,MPIU_INTEGER,rootdata,leafdata,ierr);CHKERRA(ierr);
 91:       call PetscSFBcastEnd(sf,MPIU_INTEGER,rootdata,leafdata,ierr);CHKERRA(ierr);
 92:       call PetscViewerASCIIPrintf(PETSC_VIEWER_STDOUT_WORLD,"## Bcast Rootdata\n",ierr);CHKERRA(ierr);
 93:       call PetscIntView(nrootsalloc,rootdata,PETSC_VIEWER_STDOUT_WORLD,ierr);CHKERRA(ierr);
 94:       call PetscViewerASCIIPrintf(PETSC_VIEWER_STDOUT_WORLD,"## Bcast Leafdata\n",ierr);CHKERRA(ierr);
 95:       call PetscIntView(nleavesalloc,leafdata,PETSC_VIEWER_STDOUT_WORLD,ierr);CHKERRA(ierr);

 97:       call PetscSFGetGraph(sf,gnroots,gnleaves,gmine,gremote,ierr);CHKERRA(ierr);
 98:       if (gnleaves .ne. nleaves) then; SETERRA(PETSC_COMM_WORLD,PETSC_ERR_PLIB,'nleaves returned from PetscSFGetGraph() does not match that set with PetscSFSetGraph()'); endif
 99:       do i=1,nleaves
100:          if (gmine(i) .ne. mine(i)) then; SETERRA(PETSC_COMM_WORLD,PETSC_ERR_PLIB,'Root from PetscSFGetGraph() does not match that set with PetscSFSetGraph()'); endif
101:       enddo
102:       do i=1,nleaves
103:          if (gremote(i)%index .ne. remote(i)%index) then; SETERRA(PETSC_COMM_WORLD,PETSC_ERR_PLIB,'Leaf from PetscSFGetGraph() does not match that set with PetscSFSetGraph()'); endif
104:       enddo

106: !    Clean storage for star forest.
107:       call PetscSFDestroy(sf,ierr);CHKERRA(ierr);
108:       call PetscFinalize(ierr);
109:   end

111: !/*TEST
112: !  build:
113: !    requires: define(PETSC_HAVE_FORTRAN_TYPE_STAR)
114: !
115: !  test:
116: !    nsize: 3
117: !
118: !TEST*/