Date: 2025-03-28T21:11:23+00:00

Actual source code: ex4f90.F90

      1: !
      2: !
      3: !  Description:  Illustrates the use of VecSetValues() to set
      4: !  multiple values at once; demonstrates VecGetArrayF90().
      5: !
      6: ! -----------------------------------------------------------------------

      8:       program main
      9: #include <petsc/finclude/petscvec.h>
     10:       use petscvec
     11:       implicit none

     13: ! - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
     14: !                 Beginning of program
     15: ! - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

     17:        PetscInt, parameter :: n=6
     18:        PetscScalar, dimension(n) ::  xwork
     19:        PetscScalar, pointer, dimension(:) ::  xx_v,yy_v
     20:        PetscInt, dimension(n) :: loc
     21:        PetscInt i
     22:        PetscErrorCode ierr
     23:        Vec     x,y

     25:        PetscCallA(PetscInitialize(ierr))

     27: !  Create initial vector and duplicate it

     29:        PetscCallA(VecCreateSeq(PETSC_COMM_SELF,n,x,ierr))
     30:        PetscCallA(VecDuplicate(x,y,ierr))

     32: !  Fill work arrays with vector entries and locations.  Note that
     33: !  the vector indices are 0-based in PETSc (for both Fortran and
     34: !  C vectors)

     36:        do 10 i=1,n
     37:           loc(i) = i-1
     38:           xwork(i) = 10.0*real(i)
     39:   10   continue

     41: !  Set vector values.  Note that we set multiple entries at once.
     42: !  Of course, usually one would create a work array that is the
     43: !  natural size for a particular problem (not one that is as long
     44: !  as the full vector).

     46:        PetscCallA(VecSetValues(x,n,loc,xwork,INSERT_VALUES,ierr))

     48: !  Assemble vector

     50:        PetscCallA(VecAssemblyBegin(x,ierr))
     51:        PetscCallA(VecAssemblyEnd(x,ierr))

     53: !  View vector
     54:        PetscCallA(PetscObjectSetName(x, 'initial vector:',ierr))
     55:        PetscCallA(VecView(x,PETSC_VIEWER_STDOUT_SELF,ierr))
     56:        PetscCallA(VecCopy(x,y,ierr))

     58: !  Get a pointer to vector data.
     59: !    - For default PETSc vectors, VecGetArrayF90() returns a pointer to
     60: !      the data array.  Otherwise, the routine is implementation dependent.
     61: !    - You MUST call VecRestoreArray() when you no longer need access to
     62: !      the array.

     64:        PetscCallA(VecGetArrayF90(x,xx_v,ierr))
     65:        PetscCallA(VecGetArrayF90(y,yy_v,ierr))

     67: !  Modify vector data

     69:        do 30 i=1,n
     70:           xx_v(i) = 100.0*real(i)
     71:           yy_v(i) = 1000.0*real(i)
     72:   30   continue

     74: !  Restore vectors

     76:        PetscCallA(VecRestoreArrayF90(x,xx_v,ierr))
     77:        PetscCallA(VecRestoreArrayF90(y,yy_v,ierr))

     79: !  View vectors
     80:        PetscCallA(PetscObjectSetName(x, 'new vector 1:',ierr))
     81:        PetscCallA(VecView(x,PETSC_VIEWER_STDOUT_SELF,ierr))

     83:        PetscCallA(PetscObjectSetName(y, 'new vector 2:',ierr))
     84:        PetscCallA(VecView(y,PETSC_VIEWER_STDOUT_SELF,ierr))

     86: !  Free work space.  All PETSc objects should be destroyed when they
     87: !  are no longer needed.

     89:        PetscCallA(VecDestroy(x,ierr))
     90:        PetscCallA(VecDestroy(y,ierr))
     91:        PetscCallA(PetscFinalize(ierr))
     92:        end

     94: !
     95: !/*TEST
     96: !
     97: !     test:
     98: !
     99: !TEST*/