Actual source code: ex22f.F
petsc-3.4.5 2014-06-29
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/petscdmda.h>
29: PetscErrorCode ierr
30: DM da
31: KSP ksp
32: Vec x
33: external ComputeRHS,ComputeMatrix
34: PetscInt i1,i3
35: PetscInt ctx
37: call PetscInitialize(PETSC_NULL_CHARACTER,ierr)
39: i3 = -3
40: i1 = 1
41: call KSPCreate(MPI_COMM_WORLD,ksp,ierr)
42: call DMDACreate3d(PETSC_COMM_WORLD,DMDA_BOUNDARY_NONE, &
43: & DMDA_BOUNDARY_NONE,DMDA_BOUNDARY_NONE, &
44: & DMDA_STENCIL_STAR,i3,i3,i3,PETSC_DECIDE,PETSC_DECIDE, &
45: & PETSC_DECIDE,i1,i1,PETSC_NULL_INTEGER,PETSC_NULL_INTEGER, &
46: & PETSC_NULL_INTEGER,da,ierr)
47: call KSPSetDM(ksp,da,ierr)
48: call KSPSetComputeRHS(ksp,ComputeRHS,ctx,ierr)
49: call KSPSetComputeOperators(ksp,ComputeMatrix,ctx,ierr)
51: call KSPSetFromOptions(ksp,ierr)
52: call KSPSolve(ksp,PETSC_NULL_OBJECT,PETSC_NULL_OBJECT,ierr)
53: call KSPGetSolution(ksp,x,ierr)
54: ! call VecView(x,PETSC_NULL_OBJECT,ierr)
55: call KSPDestroy(ksp,ierr)
56: call DMDestroy(da,ierr)
57: call PetscFinalize(ierr)
59: end
61: subroutine ComputeRHS(ksp,b,ctx,ierr)
62: implicit none
64: #include <finclude/petscsys.h>
65: #include <finclude/petscvec.h>
66: #include <finclude/petscdmda.h>
68: PetscErrorCode ierr
69: PetscInt mx,my,mz
70: PetscScalar h
71: Vec b
72: KSP ksp
73: DM da
74: PetscInt ctx
76: call KSPGetDM(ksp,da,ierr)
77: call DMDAGetInfo(da,PETSC_NULL_INTEGER,mx,my,mz, &
78: & PETSC_NULL_INTEGER,PETSC_NULL_INTEGER, &
79: & PETSC_NULL_INTEGER,PETSC_NULL_INTEGER, &
80: & PETSC_NULL_INTEGER,PETSC_NULL_INTEGER, &
81: & PETSC_NULL_INTEGER,PETSC_NULL_INTEGER, &
82: & PETSC_NULL_INTEGER,ierr)
83: h = 1.d0/((mx-1)*(my-1)*(mz-1))
85: call VecSet(b,h,ierr)
86: return
87: end
90: subroutine ComputeMatrix(ksp,JJ,jac,str,ctx,ierr)
91: implicit none
93: #include <finclude/petscsys.h>
94: #include <finclude/petscvec.h>
95: #include <finclude/petscmat.h>
96: #include <finclude/petscdmda.h>
98: Mat jac,JJ
99: PetscErrorCode ierr
100: KSP ksp
101: DM da
102: PetscInt i,j,k,mx,my,mz,xm
103: PetscInt ym,zm,xs,ys,zs,i1,i7
104: PetscScalar v(7),Hx,Hy,Hz
105: PetscScalar HxHydHz,HyHzdHx
106: PetscScalar HxHzdHy
107: MatStencil row(4),col(4,7)
108: MatStructure str
109: PetscInt ctx
110: i1 = 1
111: i7 = 7
112: call KSPGetDM(ksp,da,ierr)
113: call DMDAGetInfo(da,PETSC_NULL_INTEGER,mx,my,mz, &
114: & PETSC_NULL_INTEGER,PETSC_NULL_INTEGER, &
115: & PETSC_NULL_INTEGER,PETSC_NULL_INTEGER, &
116: & PETSC_NULL_INTEGER,PETSC_NULL_INTEGER, &
117: & PETSC_NULL_INTEGER,PETSC_NULL_INTEGER, &
118: & PETSC_NULL_INTEGER,ierr)
120: Hx = 1.d0 / (mx-1)
121: Hy = 1.d0 / (my-1)
122: Hz = 1.d0 / (mz-1)
123: HxHydHz = Hx*Hy/Hz
124: HxHzdHy = Hx*Hz/Hy
125: HyHzdHx = Hy*Hz/Hx
126: call DMDAGetCorners(da,xs,ys,zs,xm,ym,zm,ierr)
128: do 10,k=zs,zs+zm-1
129: do 20,j=ys,ys+ym-1
130: do 30,i=xs,xs+xm-1
131: row(MatStencil_i) = i
132: row(MatStencil_j) = j
133: row(MatStencil_k) = k
134: if (i.eq.0 .or. j.eq.0 .or. k.eq.0 .or. i.eq.mx-1 .or. &
135: & j.eq.my-1 .or. k.eq.mz-1) then
136: v(1) = 2.d0*(HxHydHz + HxHzdHy + HyHzdHx)
137: call MatSetValuesStencil(jac,i1,row,i1,row,v,INSERT_VALUES, &
138: & ierr)
139: else
140: v(1) = -HxHydHz
141: col(MatStencil_i,1) = i
142: col(MatStencil_j,1) = j
143: col(MatStencil_k,1) = k-1
144: v(2) = -HxHzdHy
145: col(MatStencil_i,2) = i
146: col(MatStencil_j,2) = j-1
147: col(MatStencil_k,2) = k
148: v(3) = -HyHzdHx
149: col(MatStencil_i,3) = i-1
150: col(MatStencil_j,3) = j
151: col(MatStencil_k,3) = k
152: v(4) = 2.d0*(HxHydHz + HxHzdHy + HyHzdHx)
153: col(MatStencil_i,4) = i
154: col(MatStencil_j,4) = j
155: col(MatStencil_k,4) = k
156: v(5) = -HyHzdHx
157: col(MatStencil_i,5) = i+1
158: col(MatStencil_j,5) = j
159: col(MatStencil_k,5) = k
160: v(6) = -HxHzdHy
161: col(MatStencil_i,6) = i
162: col(MatStencil_j,6) = j+1
163: col(MatStencil_k,6) = k
164: v(7) = -HxHydHz
165: col(MatStencil_i,7) = i
166: col(MatStencil_j,7) = j
167: col(MatStencil_k,7) = k+1
168: call MatSetValuesStencil(jac,i1,row,i7,col,v,INSERT_VALUES, &
169: & ierr)
170: endif
171: 30 continue
172: 20 continue
173: 10 continue
175: call MatAssemblyBegin(jac,MAT_FINAL_ASSEMBLY,ierr)
176: call MatAssemblyEnd(jac,MAT_FINAL_ASSEMBLY,ierr)
177: return
178: end