1: program main
  2: #include <petsc/finclude/petscvec.h>
  3: #include <petsc/finclude/petscmat.h>

  5:   use petscvec
  6:   use petscmat

  8:   implicit none

 10:   Mat A
 11:   MatPartitioning part
 12:   IS is
 13:   PetscInt   ::     i, m, N
 14:   PetscInt   ::     rstart, rend
 15:   PetscInt, pointer, dimension(:) ::   emptyranks, bigranks, cols
 16:   PetscScalar, pointer, dimension(:) :: vals
 17:   PetscInt :: &
 18:     nbigranks = 10, &
 19:     nemptyranks = 10
 20:   PetscMPIInt   ::  rank, sizef
 21:   PetscErrorCode ierr
 22:   PetscBool set
 23:   PetscInt, parameter :: zero = 0, one = 1, two = 2, three = 3

 25:   PetscCallA(PetscInitialize(ierr))

 27:   PetscCallMPIA(MPI_Comm_rank(PETSC_COMM_WORLD, rank, ierr))
 28:   PetscCallMPIA(MPI_Comm_size(PETSC_COMM_WORLD, sizef, ierr))

 30:   allocate (emptyranks(nemptyranks))
 31:   allocate (bigranks(nbigranks))

 33:   PetscCallA(PetscOptionsGetIntArray(PETSC_NULL_OPTIONS, PETSC_NULL_CHARACTER, '-emptyranks', emptyranks, nemptyranks, set, ierr))
 34:   PetscCallA(PetscOptionsGetIntArray(PETSC_NULL_OPTIONS, PETSC_NULL_CHARACTER, '-bigranks', bigranks, nbigranks, set, ierr))

 36:   m = 1
 37:   do i = 1, nemptyranks
 38:     if (rank == emptyranks(i)) m = 0
 39:   end do
 40:   do i = 1, nbigranks
 41:     if (rank == bigranks(i)) m = 5
 42:   end do

 44:   deallocate (emptyranks)
 45:   deallocate (bigranks)

 47:   PetscCallA(MatCreate(PETSC_COMM_WORLD, A, ierr))
 48:   PetscCallA(MatSetsizes(A, m, m, PETSC_DECIDE, PETSC_DECIDE, ierr))
 49:   PetscCallA(MatSetFromOptions(A, ierr))
 50:   PetscCallA(MatSeqAIJSetPreallocation(A, three, PETSC_NULL_INTEGER_ARRAY, ierr))
 51:   PetscCallA(MatMPIAIJSetPreallocation(A, three, PETSC_NULL_INTEGER_ARRAY, two, PETSC_NULL_INTEGER_ARRAY, ierr))
 52:   PetscCallA(MatSeqBAIJSetPreallocation(A, one, three, PETSC_NULL_INTEGER_ARRAY, ierr))
 53:   PetscCallA(MatMPIBAIJSetPreallocation(A, one, three, PETSC_NULL_INTEGER_ARRAY, two, PETSC_NULL_INTEGER_ARRAY, ierr))
 54:   PetscCallA(MatSeqSBAIJSetPreallocation(A, one, two, PETSC_NULL_INTEGER_ARRAY, ierr))
 55:   PetscCallA(MatMPISBAIJSetPreallocation(A, one, two, PETSC_NULL_INTEGER_ARRAY, one, PETSC_NULL_INTEGER_ARRAY, ierr))

 57:   PetscCallA(MatGetSize(A, PETSC_NULL_INTEGER, N, ierr))
 58:   PetscCallA(MatGetOwnershipRange(A, rstart, rend, ierr))

 60:   allocate (cols(1:3))
 61:   allocate (vals(1:3))
 62:   do i = rstart, rend - 1

 64:     cols = (/mod((i + N - 1), N), i, mod((i + 1), N)/)
 65:     vals = [1.0, 1.0, 1.0]
 66:     PetscCallA(MatSetValues(A, one, [i], three, cols, vals, INSERT_VALUES, ierr))
 67:   end do
 68:   deallocate (cols)
 69:   deallocate (vals)
 70:   PetscCallA(MatAssemblyBegin(A, MAT_FINAL_ASSEMBLY, ierr))
 71:   PetscCallA(MatAssemblyEnd(A, MAT_FINAL_ASSEMBLY, ierr))
 72:   PetscCallA(MatView(A, PETSC_VIEWER_STDOUT_WORLD, ierr))

 74:   PetscCallA(MatPartitioningCreate(PETSC_COMM_WORLD, part, ierr))
 75:   PetscCallA(MatPartitioningSetAdjacency(part, A, ierr))
 76:   PetscCallA(MatPartitioningSetFromOptions(part, ierr))
 77:   PetscCallA(MatPartitioningApply(part, is, ierr))
 78:   PetscCallA(ISView(is, PETSC_VIEWER_STDOUT_WORLD, ierr))
 79:   PetscCallA(ISDestroy(is, ierr))
 80:   PetscCallA(MatPartitioningDestroy(part, ierr))
 81:   PetscCallA(MatDestroy(A, ierr))
 82:   PetscCallA(PetscFinalize(ierr))

 84: end program

 86: !/*TEST
 87: !
 88: !   test:
 89: !      nsize: 8
 90: !      args: -emptyranks 0,2,4 -bigranks 1,3,7 -mat_partitioning_type average
 91: !      output_file: output/ex17_1.out
 92: !      # cannot test with external package partitioners since they produce different results on different systems
 93: !
 94: !TEST*/