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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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