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

  7: program main
  8: #include <petsc/finclude/petscvec.h>
  9:   use petscmpi  ! or mpi or mpi_f08
 10:   use petscvec
 11:   implicit none

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

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

 25:   PetscMPIInt niranks, nranks
 26:   PetscMPIInt, pointer ::       iranks(:), ranks(:)
 27:   PetscInt, pointer ::          ioffset(:), irootloc(:), roffset(:), rmine(:), rremote(:)

 29:   PetscCallA(PetscInitialize(ierr))
 30:   stride = 2
 31:   PetscCallMPIA(MPI_Comm_rank(PETSC_COMM_WORLD, rank, ierr))
 32:   PetscCallMPIA(MPI_Comm_size(PETSC_COMM_WORLD, size, ierr))

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

 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:   end if

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

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

 74: !   Allocate space for send and receive 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:   end do
 80:   do i = 1, nroots
 81:     rootdata(1 + (i - 1)*stride) = 100*(rank + 1) + i - 1
 82:   end do

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

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

 97: !     Reduce entries from leafdata to rootdata. Computation or other communication can be performed between the begin and end calls.
 98:   PetscCallA(PetscSFReduceBegin(sf, MPIU_INTEGER, leafdata, rootdata, MPI_SUM, ierr))
 99:   PetscCallA(PetscSFReduceEnd(sf, MPIU_INTEGER, leafdata, rootdata, MPI_SUM, ierr))
100:   PetscCallA(PetscViewerASCIIPrintf(PETSC_VIEWER_STDOUT_WORLD, '## Reduce Leafdata\n', ierr))
101:   PetscCallA(PetscIntView(nleavesalloc, leafdata, PETSC_VIEWER_STDOUT_WORLD, ierr))
102:   PetscCallA(PetscViewerASCIIPrintf(PETSC_VIEWER_STDOUT_WORLD, '## Reduce Rootdata\n', ierr))
103:   PetscCallA(PetscIntView(nrootsalloc, rootdata, PETSC_VIEWER_STDOUT_WORLD, ierr))

105:   PetscCallA(PetscSFGetGraph(sf, gnroots, gnleaves, gmine, gremote, ierr))
106:   PetscCheckA(gnleaves == nleaves, PETSC_COMM_WORLD, PETSC_ERR_PLIB, 'nleaves returned from PetscSFGetGraph() does not match that set with PetscSFSetGraph()')
107:   do i = 1, nleaves
108:     PetscCheckA(gmine(i) == mine(i), PETSC_COMM_WORLD, PETSC_ERR_PLIB, 'Root from PetscSFGetGraph() does not match that set with PetscSFSetGraph()')
109:   end do
110:   do i = 1, nleaves
111:     PetscCheckA(gremote(i)%index == remote(i)%index, PETSC_COMM_WORLD, PETSC_ERR_PLIB, 'Leaf from PetscSFGetGraph() does not match that set with PetscSFSetGraph()')
112:   end do
113:   PetscCallA(PetscSFRestoreGraph(sf, gnroots, gnleaves, gmine, gremote, ierr))

115: ! Test PetscSFGet{Leaf,Root}Ranks
116:   PetscCallA(PetscSFGetLeafRanks(sf, niranks, iranks, ioffset, irootloc, ierr))
117:   PetscCallA(PetscSFGetRootRanks(sf, nranks, ranks, roffset, rmine, rremote, ierr))

119: !    Clean storage for star forest.
120:   PetscCallA(PetscSFDestroy(sf, ierr))

122: !  Create a star forest with continuous leaves and hence no buffer
123:   PetscCallA(PetscSFCreate(PETSC_COMM_WORLD, sf, ierr))
124:   PetscCallA(PetscSFSetFromOptions(sf, ierr))
125:   PetscCallA(PetscSFSetGraph(sf, nrootsalloc, nleaves, PETSC_NULL_INTEGER_ARRAY, PETSC_COPY_VALUES, remote, PETSC_COPY_VALUES, ierr))
126:   PetscCallA(PetscSFSetUp(sf, ierr))

128: !   View graph, mostly useful for debugging purposes.
129:   PetscCallA(PetscViewerPushFormat(PETSC_VIEWER_STDOUT_WORLD, PETSC_VIEWER_ASCII_INFO_DETAIL, ierr))
130:   PetscCallA(PetscSFView(sf, PETSC_VIEWER_STDOUT_WORLD, ierr))
131:   PetscCallA(PetscViewerPopFormat(PETSC_VIEWER_STDOUT_WORLD, ierr))

133:   PetscCallA(PetscSFGetGraph(sf, gnroots, gnleaves, gmine, gremote, ierr))
134:   PetscCheckA(loc(gmine) == loc(PETSC_NULL_INTEGER), PETSC_COMM_WORLD, PETSC_ERR_PLIB, 'Leaves from PetscSFGetGraph() not null as expected')
135:   PetscCallA(PetscSFRestoreGraph(sf, gnroots, gnleaves, gmine, gremote, ierr))
136:   PetscCallA(PetscSFDestroy(sf, ierr))
137:   PetscCallA(PetscFinalize(ierr))
138: end

140: !/*TEST
141: !  build:
142: !    requires: defined(PETSC_HAVE_FORTRAN_TYPE_STAR)
143: !
144: !  test:
145: !    nsize: 3
146: !
147: !TEST*/