1: #include <petsc/finclude/petscvec.h>
  2: program main
  3:   use petscvec
  4:   implicit none

  6:   PetscErrorCode ::ierr
  7:   PetscMPIInt ::   rank, size
  8:   PetscInt :: i, m, low, high, ldim, iglobal
  9:   PetscScalar :: v
 10:   Vec ::         u
 11:   PetscViewer :: viewer
 12: #if defined(PETSC_USE_LOG)
 13:   PetscClassId classid
 14: #endif

 16:   PetscBool :: flg
 17: #if defined(PETSC_USE_LOG)
 18:   PetscLogEvent VECTOR_GENERATE, VECTOR_READ
 19: #endif

 21:   PetscCallA(PetscInitialize(ierr))

 23:   PetscCallMPIA(MPI_Comm_rank(PETSC_COMM_WORLD, rank, ierr))

 25:   PetscCallMPIA(MPI_Comm_size(PETSC_COMM_WORLD, size, ierr))  !gives number of processes in the group of comm (integer)
 26:   m = 10
 27:   PetscCallA(PetscOptionsGetInt(PETSC_NULL_OPTIONS, PETSC_NULL_CHARACTER, '-m', m, flg, ierr)) !gives the integer value for a particular option in the database.

 29:   ! PART 1:  Generate vector, then write it in binary format */

 31: #if defined(PETSC_USE_LOG)
 32:   PetscCallA(PetscLogEventRegister('Generate Vector', classid, VECTOR_GENERATE, ierr))
 33:   PetscCallA(PetscLogEventBegin(VECTOR_GENERATE, ierr))
 34: #endif
 35:   ! Create vector
 36:   PetscCallA(VecCreate(PETSC_COMM_WORLD, u, ierr))
 37:   PetscCallA(VecSetSizes(u, PETSC_DECIDE, m, ierr))
 38:   PetscCallA(VecSetFromOptions(u, ierr))
 39:   PetscCallA(VecGetOwnershipRange(u, low, high, ierr))
 40:   PetscCallA(VecGetLocalSize(u, ldim, ierr))
 41:   do i = 0, ldim - 1
 42:     iglobal = i + low
 43:     v = real(i + 100*rank)
 44:     PetscCallA(VecSetValues(u, 1_PETSC_INT_KIND, [iglobal], [v], INSERT_VALUES, ierr))
 45:   end do
 46:   PetscCallA(VecAssemblyBegin(u, ierr))
 47:   PetscCallA(VecAssemblyEnd(u, ierr))
 48:   PetscCallA(VecView(u, PETSC_VIEWER_STDOUT_WORLD, ierr))

 50:   PetscCallA(PetscPrintf(PETSC_COMM_WORLD, 'writing vector in binary to vector.dat ...\n', ierr))
 51:   PetscCallA(PetscViewerBinaryOpen(PETSC_COMM_WORLD, 'vector.dat', FILE_MODE_WRITE, viewer, ierr))
 52:   PetscCallA(VecView(u, viewer, ierr))
 53:   PetscCallA(PetscViewerDestroy(viewer, ierr))
 54:   PetscCallA(VecDestroy(u, ierr))
 55:   PetscCallA(PetscOptionsSetValue(PETSC_NULL_OPTIONS, '-viewer_binary_mpiio', PETSC_NULL_CHARACTER, ierr))

 57: #if defined(PETSC_USE_LOG)
 58:   PetscCallA(PetscLogEventEnd(VECTOR_GENERATE, ierr))
 59: #endif

 61:   ! PART 2:  Read in vector in binary format

 63:   ! Read new vector in binary format
 64: #if defined(PETSC_USE_LOG)
 65:   PetscCallA(PetscLogEventRegister('Read Vector', classid, VECTOR_READ, ierr))
 66:   PetscCallA(PetscLogEventBegin(VECTOR_READ, ierr))
 67: #endif
 68:   PetscCallA(PetscPrintf(PETSC_COMM_WORLD, 'reading vector in binary from vector.dat ...\n', ierr))
 69:   PetscCallA(PetscViewerBinaryOpen(PETSC_COMM_WORLD, 'vector.dat', FILE_MODE_READ, viewer, ierr))
 70:   PetscCallA(VecCreate(PETSC_COMM_WORLD, u, ierr))
 71:   PetscCallA(VecLoad(u, viewer, ierr))
 72:   PetscCallA(PetscViewerDestroy(viewer, ierr))

 74: #if defined(PETSC_USE_LOG)
 75:   PetscCallA(PetscLogEventEnd(VECTOR_READ, ierr))
 76: #endif
 77:   PetscCallA(VecView(u, PETSC_VIEWER_STDOUT_WORLD, ierr))

 79:   ! Free data structures
 80:   PetscCallA(VecDestroy(u, ierr))
 81:   PetscCallA(PetscFinalize(ierr))

 83: end program

 85: !/*TEST
 86: !
 87: !     test:
 88: !       nsize: 1
 89: !       requires: mpiio
 90: !       output_file: output/ex5_1.out
 91: !
 92: !     test:
 93: !       suffix: 2
 94: !       nsize: 2
 95: !       requires: mpiio
 96: !       output_file: output/ex5_2.out
 97: !
 98: !TEST*/