Actual source code: ex22f.F

petsc-3.5.2 2014-09-08
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  1: !
  2: !   Laplacian in 3D. Modeled by the partial differential equation
  3: !
  4: !   Laplacian u = 1,0 < x,y,z < 1,
  5: !
  6: !   with boundary conditions
  7: !
  8: !   u = 1 for x = 0, x = 1, y = 0, y = 1, z = 0, z = 1.
  9: !
 10: !   This uses multigrid to solve the linear system

 12:       program main
 13:       implicit none

 15: ! - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 16: !                    Include files
 17: ! - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 18: !
 19: !     petscsys.h  - base PETSc routines      petscvec.h - vectors
 20: !     petscmat.h - matrices
 21: !     petscksp.h    - Krylov subspace methods  petscpc.h  - preconditioners

 23: #include <finclude/petscsys.h>
 24: #include <finclude/petscvec.h>
 25: #include <finclude/petscmat.h>
 26: #include <finclude/petscpc.h>
 27: #include <finclude/petscksp.h>
 28: #include <finclude/petscdm.h>
 29: #include <finclude/petscdmda.h>
 30:       PetscErrorCode   ierr
 31:       DM               da
 32:       KSP              ksp
 33:       Vec              x
 34:       external         ComputeRHS,ComputeMatrix
 35:       PetscInt i1,i3
 36:       PetscInt         ctx

 38:       call  PetscInitialize(PETSC_NULL_CHARACTER,ierr)

 40:       i3 = -3
 41:       i1 = 1
 42:       call KSPCreate(MPI_COMM_WORLD,ksp,ierr)
 43:       call DMDACreate3d(PETSC_COMM_WORLD,DM_BOUNDARY_NONE,              &
 44:      &    DM_BOUNDARY_NONE,DM_BOUNDARY_NONE,                               &
 45:      &    DMDA_STENCIL_STAR,i3,i3,i3,PETSC_DECIDE,PETSC_DECIDE,                        &
 46:      &    PETSC_DECIDE,i1,i1,PETSC_NULL_INTEGER,PETSC_NULL_INTEGER,                        &
 47:      &                PETSC_NULL_INTEGER,da,ierr)
 48:       call KSPSetDM(ksp,da,ierr)
 49:       call KSPSetComputeRHS(ksp,ComputeRHS,ctx,ierr)
 50:       call KSPSetComputeOperators(ksp,ComputeMatrix,ctx,ierr)

 52:       call KSPSetFromOptions(ksp,ierr)
 53:       call KSPSolve(ksp,PETSC_NULL_OBJECT,PETSC_NULL_OBJECT,ierr)
 54:       call KSPGetSolution(ksp,x,ierr)
 55: !      call VecView(x,PETSC_NULL_OBJECT,ierr)
 56:       call KSPDestroy(ksp,ierr)
 57:       call DMDestroy(da,ierr)
 58:       call PetscFinalize(ierr)

 60:       end

 62:       subroutine ComputeRHS(ksp,b,ctx,ierr)
 63:       implicit none

 65: #include <finclude/petscsys.h>
 66: #include <finclude/petscvec.h>
 67: #include <finclude/petscdm.h>
 68: #include <finclude/petscdmda.h>

 70:       PetscErrorCode  ierr
 71:       PetscInt mx,my,mz
 72:       PetscScalar  h
 73:       Vec          b
 74:       KSP          ksp
 75:       DM           da
 76:       PetscInt     ctx

 78:       call KSPGetDM(ksp,da,ierr)
 79:       call DMDAGetInfo(da,PETSC_NULL_INTEGER,mx,my,mz,                        &
 80:      &               PETSC_NULL_INTEGER,PETSC_NULL_INTEGER,                 &
 81:      &               PETSC_NULL_INTEGER,PETSC_NULL_INTEGER,                 &
 82:      &               PETSC_NULL_INTEGER,PETSC_NULL_INTEGER,                 &
 83:      &               PETSC_NULL_INTEGER,PETSC_NULL_INTEGER,                 &
 84:      &               PETSC_NULL_INTEGER,ierr)
 85:       h    = 1.d0/((mx-1)*(my-1)*(mz-1))

 87:       call VecSet(b,h,ierr)
 88:       return
 89:       end


 92:       subroutine ComputeMatrix(ksp,JJ,jac,ctx,ierr)
 93:       implicit none

 95: #include <finclude/petscsys.h>
 96: #include <finclude/petscvec.h>
 97: #include <finclude/petscmat.h>
 98: #include <finclude/petscdm.h>
 99: #include <finclude/petscdmda.h>

101:       Mat          jac,JJ
102:       PetscErrorCode    ierr
103:       KSP          ksp
104:       DM           da
105:       PetscInt    i,j,k,mx,my,mz,xm
106:       PetscInt    ym,zm,xs,ys,zs,i1,i7
107:       PetscScalar  v(7),Hx,Hy,Hz
108:       PetscScalar  HxHydHz,HyHzdHx
109:       PetscScalar  HxHzdHy
110:       MatStencil   row(4),col(4,7)
111:       PetscInt     ctx
112:       i1 = 1
113:       i7 = 7
114:       call KSPGetDM(ksp,da,ierr)
115:       call DMDAGetInfo(da,PETSC_NULL_INTEGER,mx,my,mz,                       &
116:      &               PETSC_NULL_INTEGER,PETSC_NULL_INTEGER,                &
117:      &               PETSC_NULL_INTEGER,PETSC_NULL_INTEGER,                &
118:      &               PETSC_NULL_INTEGER,PETSC_NULL_INTEGER,                &
119:      &               PETSC_NULL_INTEGER,PETSC_NULL_INTEGER,                &
120:      &               PETSC_NULL_INTEGER,ierr)

122:       Hx = 1.d0 / (mx-1)
123:       Hy = 1.d0 / (my-1)
124:       Hz = 1.d0 / (mz-1)
125:       HxHydHz = Hx*Hy/Hz
126:       HxHzdHy = Hx*Hz/Hy
127:       HyHzdHx = Hy*Hz/Hx
128:       call DMDAGetCorners(da,xs,ys,zs,xm,ym,zm,ierr)

130:       do 10,k=zs,zs+zm-1
131:         do 20,j=ys,ys+ym-1
132:           do 30,i=xs,xs+xm-1
133:           row(MatStencil_i) = i
134:           row(MatStencil_j) = j
135:           row(MatStencil_k) = k
136:           if (i.eq.0 .or. j.eq.0 .or. k.eq.0 .or. i.eq.mx-1 .or.         &
137:      &         j.eq.my-1 .or. k.eq.mz-1) then
138:             v(1) = 2.d0*(HxHydHz + HxHzdHy + HyHzdHx)
139:             call MatSetValuesStencil(jac,i1,row,i1,row,v,INSERT_VALUES,    &
140:      &                               ierr)
141:           else
142:             v(1) = -HxHydHz
143:              col(MatStencil_i,1) = i
144:              col(MatStencil_j,1) = j
145:              col(MatStencil_k,1) = k-1
146:             v(2) = -HxHzdHy
147:              col(MatStencil_i,2) = i
148:              col(MatStencil_j,2) = j-1
149:              col(MatStencil_k,2) = k
150:             v(3) = -HyHzdHx
151:              col(MatStencil_i,3) = i-1
152:              col(MatStencil_j,3) = j
153:              col(MatStencil_k,3) = k
154:             v(4) = 2.d0*(HxHydHz + HxHzdHy + HyHzdHx)
155:              col(MatStencil_i,4) = i
156:              col(MatStencil_j,4) = j
157:              col(MatStencil_k,4) = k
158:             v(5) = -HyHzdHx
159:              col(MatStencil_i,5) = i+1
160:              col(MatStencil_j,5) = j
161:              col(MatStencil_k,5) = k
162:             v(6) = -HxHzdHy
163:              col(MatStencil_i,6) = i
164:              col(MatStencil_j,6) = j+1
165:              col(MatStencil_k,6) = k
166:             v(7) = -HxHydHz
167:              col(MatStencil_i,7) = i
168:              col(MatStencil_j,7) = j
169:              col(MatStencil_k,7) = k+1
170:       call MatSetValuesStencil(jac,i1,row,i7,col,v,INSERT_VALUES,               &
171:      &                               ierr)
172:           endif
173:  30       continue
174:  20     continue
175:  10   continue

177:       call MatAssemblyBegin(jac,MAT_FINAL_ASSEMBLY,ierr)
178:       call MatAssemblyEnd(jac,MAT_FINAL_ASSEMBLY,ierr)
179:       return
180:       end