Date: 2021-03-03T22:27:03+00:00

Actual source code: ex13f90aux.F90
petsc-3.14.5 2021-03-03
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      1: module ex13f90aux
      2:   implicit none
      3: contains
      4:   !
      5:   ! A subroutine which returns the boundary conditions.
      6:   !
      7:   subroutine get_boundary_cond(b_x,b_y,b_z)
      8: #include <petsc/finclude/petscdm.h>
      9:     use petscdm
     10:     DMBoundaryType,intent(inout) :: b_x,b_y,b_z

     12:     ! Here you may set the BC types you want
     13:     b_x = DM_BOUNDARY_GHOSTED
     14:     b_y = DM_BOUNDARY_GHOSTED
     15:     b_z = DM_BOUNDARY_GHOSTED

     17:   end subroutine get_boundary_cond
     18:   !
     19:   ! A function which returns the RHS of the equation we are solving
     20:   !
     21:   function dfdt_vdp(t,dt,ib1,ibn,jb1,jbn,kb1,kbn,imax,jmax,kmax,n,f)
     22:     !
     23:     ! Right-hand side for the van der Pol oscillator.  Very simple system of two
     24:     ! ODEs.  See Iserles, eq (5.2).
     25:     !
     26:     PetscReal, intent(in) :: t,dt
     27:     PetscInt, intent(in) :: ib1,ibn,jb1,jbn,kb1,kbn,imax,jmax,kmax,n
     28:     PetscReal, dimension(n,ib1:ibn,jb1:jbn,kb1:kbn), intent(inout) :: f
     29:     PetscReal, dimension(n,imax,jmax,kmax) :: dfdt_vdp
     30:     PetscReal, parameter :: mu=1.4, one=1.0
     31:     !
     32:     dfdt_vdp(1,:,:,:) = f(2,1,1,1)
     33:     dfdt_vdp(2,:,:,:) = mu*(one - f(1,1,1,1)**2)*f(2,1,1,1) - f(1,1,1,1)
     34:   end function dfdt_vdp
     35:   !
     36:   ! The standard Forward Euler time-stepping method.
     37:   !
     38:   recursive subroutine forw_euler(t,dt,ib1,ibn,jb1,jbn,kb1,kbn,imax,jmax,kmax,neq,y,dfdt)
     39:     PetscReal, intent(in) :: t,dt
     40:     PetscInt, intent(in) :: ib1,ibn,jb1,jbn,kb1,kbn,imax,jmax,kmax,neq
     41:     PetscReal, dimension(neq,ib1:ibn,jb1:jbn,kb1:kbn), intent(inout) :: y
     42:     !
     43:     ! Define the right-hand side function
     44:     !
     45:     interface
     46:       function dfdt(t,dt,ib1,ibn,jb1,jbn,kb1,kbn,imax,jmax,kmax,n,f)
     47:         PetscReal, intent(in) :: t,dt
     48:         PetscInt, intent(in) :: ib1,ibn,jb1,jbn,kb1,kbn,imax,jmax,kmax,n
     49:         PetscReal, dimension(n,ib1:ibn,jb1:jbn,kb1:kbn), intent(inout) :: f
     50:         PetscReal, dimension(n,imax,jmax,kmax) :: dfdt
     51:       end function dfdt
     52:     end interface
     53:     !--------------------------------------------------------------------------
     54:     !
     55:     y(:,1:imax,1:jmax,1:kmax) = y(:,1:imax,1:jmax,1:kmax)  + dt*dfdt(t,dt,ib1,ibn,jb1,jbn,kb1,kbn,imax,jmax,kmax,neq,y)
     56:   end subroutine forw_euler
     57:   !
     58:   ! The following 4 subroutines handle the mapping of coordinates. I'll explain
     59:   ! this in detail:
     60:   !    PETSc gives you local arrays which are indexed using the global indices.
     61:   ! This is probably handy in some cases, but when you are re-writing an
     62:   ! existing serial code and want to use DMDAs, you have tons of loops going
     63:   ! from 1 to imax etc. that you don't want to change.
     64:   !    These subroutines re-map the arrays so that all the local arrays go from
     65:   ! 1 to the (local) imax.
     66:   !
     67:   subroutine petsc_to_local(da,vec,array,f,dof,stw)
     68:     use petscdmda
     69:     DM                                                            :: da
     70:     Vec,intent(in)                                                :: vec
     71:     PetscReal, pointer                                            :: array(:,:,:,:)
     72:     PetscInt,intent(in)                                           :: dof,stw
     73:     PetscReal, intent(inout), dimension(:,1-stw:,1-stw:,1-stw:) :: f
     74:     PetscErrorCode                                                :: ierr
     75:     !
     76:     call DMDAVecGetArrayF90(da,vec,array,ierr);
     77:     call transform_petsc_us(array,f,stw)
     78:   end subroutine petsc_to_local
     79:   subroutine transform_petsc_us(array,f,stw)
     80:     !Note: this assumed shape-array is what does the "coordinate transformation"
     81:     PetscInt,intent(in)                                   :: stw
     82:     PetscReal, intent(in), dimension(:,1-stw:,1-stw:,1-stw:)  :: array
     83:     PetscReal,intent(inout),dimension(:,1-stw:,1-stw:,1-stw:) :: f
     84:     f(:,:,:,:) = array(:,:,:,:)
     85:   end subroutine transform_petsc_us
     86:   subroutine local_to_petsc(da,vec,array,f,dof,stw)
     87:     use petscdmda
     88:     DM                                                    :: da
     89:     Vec,intent(inout)                                     :: vec
     90:     PetscReal, pointer                                    :: array(:,:,:,:)
     91:     PetscInt,intent(in)                                    :: dof,stw
     92:     PetscReal,intent(inout),dimension(:,1-stw:,1-stw:,1-stw:)  :: f
     93:     PetscErrorCode                                        :: ierr
     94:     call transform_us_petsc(array,f,stw)
     95:     call DMDAVecRestoreArrayF90(da,vec,array,ierr);
     96:   end subroutine local_to_petsc
     97:   subroutine transform_us_petsc(array,f,stw)
     98:     !Note: this assumed shape-array is what does the "coordinate transformation"
     99:     PetscInt,intent(in)                                     :: stw
    100:     PetscReal, intent(inout), dimension(:,1-stw:,1-stw:,1-stw:) :: array
    101:     PetscReal, intent(in),dimension(:,1-stw:,1-stw:,1-stw:)      :: f
    102:     array(:,:,:,:) = f(:,:,:,:)
    103:   end subroutine transform_us_petsc
    104: end module ex13f90aux