Date: 2026-03-01T05:25:27+00:00

Actual source code: ex5f.F90

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

      6:   PetscErrorCode ::ierr
      7:   PetscMPIInt ::   rank, size
      8:   PetscInt :: i
      9:   PetscInt, parameter :: one = 1
     10:   PetscInt :: m = 10
     11:   PetscInt :: low, high, ldim, iglobal
     12:   PetscScalar :: v
     13:   Vec ::         u
     14:   PetscViewer :: viewer
     15: #if defined(PETSC_USE_LOG)
     16:   PetscClassId classid
     17: #endif

     19:   PetscBool :: flg
     20: #if defined(PETSC_USE_LOG)
     21:   PetscLogEvent VECTOR_GENERATE, VECTOR_READ
     22: #endif

     24:   PetscCallA(PetscInitialize(ierr))

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

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

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

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

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

     59: #if defined(PETSC_USE_LOG)
     60:   PetscCallA(PetscLogEventEnd(VECTOR_GENERATE, ierr))
     61: #endif

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

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

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

     81:   ! Free data structures
     82:   PetscCallA(VecDestroy(u, ierr))
     83:   PetscCallA(PetscFinalize(ierr))

     85: end program

     87: !/*TEST
     88: !
     89: !     test:
     90: !       nsize: 1
     91: !       requires: mpiio
     92: !       output_file: output/ex5_1.out
     93: !
     94: !     test:
     95: !       suffix: 2
     96: !       nsize: 2
     97: !       requires: mpiio
     98: !       output_file: output/ex5_2.out
     99: !
    100: !TEST*/