Actual source code: ex4f.F

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

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

 13: ! - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 14: !                   Macro definitions
 15: ! - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 16: !
 17: !  Macros to make clearer the process of setting values in vectors and
 18: !  getting values from vectors.
 19: !
 20: !   - The element xx_a(ib) is element ib+1 in the vector x
 21: !   - Here we add 1 to the base array index to facilitate the use of
 22: !     conventional Fortran 1-based array indexing.
 23: !
 24: #define xx_a(ib)  xx_v(xx_i + (ib))
 25: #define yy_a(ib)  yy_v(yy_i + (ib))

 27: ! - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 28: !                 Beginning of program
 29: ! - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

 31:        PetscScalar xwork(6)
 32:        PetscScalar xx_v(1),yy_v(1)
 33:        PetscInt     i,n,loc(6),isix
 34:        PetscErrorCode ierr
 35:        PetscOffset xx_i,yy_i
 36:        Vec         x,y

 38:        call PetscInitialize(PETSC_NULL_CHARACTER,ierr)
 39:        if (ierr .ne. 0) then
 40:          print*,'PetscInitialize failed'
 41:          stop
 42:        endif
 43:        n = 6
 44:        isix = 6

 46: !  Create initial vector and duplicate it

 48:        call VecCreateSeq(PETSC_COMM_SELF,n,x,ierr)
 49:        call VecDuplicate(x,y,ierr)

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

 55:        do 10 i=1,n
 56:           loc(i) = i-1
 57:           xwork(i) = 10.0*real(i)
 58:   10   continue

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

 65:        call VecSetValues(x,isix,loc,xwork,INSERT_VALUES,ierr)

 67: !  Assemble vector

 69:        call VecAssemblyBegin(x,ierr)
 70:        call VecAssemblyEnd(x,ierr)

 72: !  View vector
 73:        call PetscObjectSetName(x, 'initial vector:',ierr)
 74:        call VecView(x,PETSC_VIEWER_STDOUT_SELF,ierr)
 75:        call VecCopy(x,y,ierr)

 77: !  Get a pointer to vector data.
 78: !    - For default PETSc vectors, VecGetArray() returns a pointer to
 79: !      the data array.  Otherwise, the routine is implementation dependent.
 80: !    - You MUST call VecRestoreArray() when you no longer need access to
 81: !      the array.
 82: !    - Note that the Fortran interface to VecGetArray() differs from the
 83: !      C version.  See the users manual for details.

 85:        call VecGetArray(x,xx_v,xx_i,ierr)
 86:        call VecGetArray(y,yy_v,yy_i,ierr)

 88: !  Modify vector data

 90:        do 30 i=1,n
 91:           xx_a(i) = 100.0*real(i)
 92:           yy_a(i) = 1000.0*real(i)
 93:   30   continue

 95: !  Restore vectors

 97:        call VecRestoreArray(x,xx_v,xx_i,ierr)
 98:        call VecRestoreArray(y,yy_v,yy_i,ierr)

100: !  View vectors
101:        call PetscObjectSetName(x, 'new vector 1:',ierr)
102:        call VecView(x,PETSC_VIEWER_STDOUT_SELF,ierr)

104:        call PetscObjectSetName(y, 'new vector 2:',ierr)
105:        call VecView(y,PETSC_VIEWER_STDOUT_SELF,ierr)

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

110:        call VecDestroy(x,ierr)
111:        call VecDestroy(y,ierr)
112:        call PetscFinalize(ierr)
113:        end

115: !/*TEST
116: !
117: !     test:
118: !
119: !TEST*/