Actual source code: ex12.F
1: !
2: ! "$Id: ex12.F,v 1.60 2001/08/07 03:04:13 balay Exp $";
3: !
4: ! This example demonstrates basic use of the SNES Fortran interface.
5: !
6: ! Note: The program ex10.f is the same as this example, except that it
7: ! uses the Fortran .f suffix rather than the .F suffix.
8: !
9: ! In this example the application context is a Fortran integer array:
10: ! ctx(1) = da - distributed array
11: ! 2 = F - global vector where the function is stored
12: ! 3 = xl - local work vector
13: ! 4 = rank - processor rank
14: ! 5 = size - number of processors
15: ! 6 = N - system size
16: !
17: ! Note: Any user-defined Fortran routines (such as FormJacobian)
18: ! MUST be declared as external.
19: !
20: !
21: ! Macros to make setting/getting values into vector clearer.
22: ! The element xx(ib) is the ibth element in the vector indicated by ctx(3)
23: #define xx(ib) vxx(ixx + (ib))
24: #define ff(ib) vff(iff + (ib))
25: #define F2(ib) vF2(iF2 + (ib))
26: program main
27: implicit none
29: #include include/finclude/petsc.h
30: #include include/finclude/petscvec.h
31: #include include/finclude/petscda.h
32: #include include/finclude/petscmat.h
33: #include include/finclude/petscsnes.h
35: PetscFortranAddr ctx(6)
36: integer rank,size,ierr,N,start,end,nn,i,ii,its,flg
37: SNES snes
38: Mat J
39: Vec x,r,u
40: PetscScalar xp,FF,UU,h
41: character*(10) matrixname
42: external FormJacobian,FormFunction
44: call PetscInitialize(PETSC_NULL_CHARACTER,ierr)
45: N = 10
46: call PetscOptionsGetInt(PETSC_NULL_CHARACTER,'-n',N,flg,ierr)
47: h = 1.d0/(N-1.d0)
48: ctx(6) = N
50: call MPI_Comm_rank(PETSC_COMM_WORLD,rank,ierr)
51: call MPI_Comm_size(PETSC_COMM_WORLD,size,ierr)
52: ctx(4) = rank
53: ctx(5) = size
55: ! Set up data structures
56: call DACreate1d(PETSC_COMM_WORLD,DA_NONPERIODIC,N,1,1, &
57: & PETSC_NULL_INTEGER,ctx(1),ierr)
59: call DACreateGlobalVector(ctx(1),x,ierr)
60: call DACreateLocalVector(ctx(1),ctx(3),ierr)
62: call PetscObjectSetName(x,'Approximate Solution',ierr)
63: call VecDuplicate(x,r,ierr)
64: call VecDuplicate(x,ctx(2),ierr)
65: call VecDuplicate(x,U,ierr)
66: call PetscObjectSetName(U,'Exact Solution',ierr)
68: call MatCreateMPIAIJ(PETSC_COMM_WORLD,PETSC_DECIDE,PETSC_DECIDE,N, &
69: & N,3,PETSC_NULL_INTEGER,0,PETSC_NULL_INTEGER,J,ierr)
71: call MatGetType(J,matrixname,ierr)
73: ! Store right-hand-side of PDE and exact solution
74: call VecGetOwnershipRange(x,start,end,ierr)
75: xp = h*start
76: nn = end - start
77: ii = start
78: do 10, i=0,nn-1
79: FF = 6.0*xp + (xp+1.e-12)**6.e0
80: UU = xp*xp*xp
81: call VecSetValues(ctx(2),1,ii,FF,INSERT_VALUES,ierr)
82: call VecSetValues(U,1,ii,UU,INSERT_VALUES,ierr)
83: xp = xp + h
84: ii = ii + 1
85: 10 continue
86: call VecAssemblyBegin(ctx(2),ierr)
87: call VecAssemblyEnd(ctx(2),ierr)
88: call VecAssemblyBegin(U,ierr)
89: call VecAssemblyEnd(U,ierr)
91: ! Create nonlinear solver
92: call SNESCreate(PETSC_COMM_WORLD,snes,ierr)
94: ! Set various routines and options
95: call SNESSetFunction(snes,r,FormFunction,ctx,ierr)
96: call SNESSetJacobian(snes,J,J,FormJacobian,ctx,ierr)
97: call SNESSetFromOptions(snes,ierr)
99: ! Solve nonlinear system
100: call FormInitialGuess(snes,x,ierr)
101: call SNESSolve(snes,x,its,ierr)
103: ! Write results if first processor
104: if (ctx(4) .eq. 0) then
105: write(6,100) its
106: endif
107: 100 format('Number of Newton iterations = ',i5)
109: ! Free work space. All PETSc objects should be destroyed when they
110: ! are no longer needed.
111: call VecDestroy(x,ierr)
112: call VecDestroy(ctx(3),ierr)
113: call VecDestroy(r,ierr)
114: call VecDestroy(U,ierr)
115: call VecDestroy(ctx(2),ierr)
116: call MatDestroy(J,ierr)
117: call SNESDestroy(snes,ierr)
118: call DADestroy(ctx(1),ierr)
119: call PetscFinalize(ierr)
120: end
123: ! -------------------- Evaluate Function F(x) ---------------------
125: subroutine FormFunction(snes,x,f,ctx,ierr)
126: implicit none
127: SNES snes
128: Vec x,f
129: PetscFortranAddr ctx(*)
130: integer rank,size,i,s,n,ierr
131: PetscOffset ixx,iff,iF2
132: PetscScalar h,d,vf2(1),vxx(1),vff(1)
133: #include include/finclude/petsc.h
134: #include include/finclude/petscvec.h
135: #include include/finclude/petscda.h
136: #include include/finclude/petscmat.h
137: #include include/finclude/petscsnes.h
140: rank = ctx(4)
141: size = ctx(5)
142: h = 1.d0/(ctx(6) - 1.d0)
143: call DAGlobalToLocalBegin(ctx(1),x,INSERT_VALUES,ctx(3),ierr)
144: call DAGlobalToLocalEnd(ctx(1),x,INSERT_VALUES,ctx(3),ierr)
146: call VecGetLocalSize(ctx(3),n,ierr)
147: if (n .gt. 1000) then
148: print*, 'Local work array not big enough'
149: call MPI_Abort(PETSC_COMM_WORLD,0,ierr)
150: endif
152: !
153: ! This sets the index ixx so that vxx(ixx+1) is the first local
154: ! element in the vector indicated by ctx(3).
155: !
156: call VecGetArray(ctx(3),vxx,ixx,ierr)
157: call VecGetArray(f,vff,iff,ierr)
158: call VecGetArray(ctx(2),vF2,iF2,ierr)
160: d = h*h
162: !
163: ! Note that the array vxx() was obtained from a ghosted local vector
164: ! ctx(3) while the array vff() was obtained from the non-ghosted parallel
165: ! vector F. This is why there is a need for shift variable s. Since vff()
166: ! does not have locations for the ghost variables we need to index in it
167: ! slightly different then indexing into vxx(). For example on processor
168: ! 1 (the second processor)
169: !
170: ! xx(1) xx(2) xx(3) .....
171: ! ^^^^^^^ ^^^^^ ^^^^^
172: ! ghost value 1st local value 2nd local value
173: !
174: ! ff(1) ff(2)
175: ! ^^^^^^^ ^^^^^^^
176: ! 1st local value 2nd local value
177: !
178: if (rank .eq. 0) then
179: s = 0
180: ff(1) = xx(1)
181: else
182: s = 1
183: endif
185: do 10 i=1,n-2
186: ff(i-s+1) = d*(xx(i) - 2.d0*xx(i+1) &
187: & + xx(i+2)) + xx(i+1)*xx(i+1) &
188: & - F2(i-s+1)
189: 10 continue
191: if (rank .eq. size-1) then
192: ff(n-s) = xx(n) - 1.d0
193: endif
195: call VecRestoreArray(f,vff,iff,ierr)
196: call VecRestoreArray(ctx(3),vxx,ixx,ierr)
197: call VecRestoreArray(ctx(2),vF2,iF2,ierr)
198: return
199: end
201: ! -------------------- Form initial approximation -----------------
203: subroutine FormInitialGuess(snes,x,ierr)
204: implicit none
205: #include include/finclude/petsc.h
206: #include include/finclude/petscvec.h
207: #include include/finclude/petscsnes.h
208: integer ierr
209: Vec x
210: SNES snes
211: PetscScalar five
213: five = 5.d-1
214: call VecSet(five,x,ierr)
215: return
216: end
218: ! -------------------- Evaluate Jacobian --------------------
220: subroutine FormJacobian(snes,x,jac,B,flag,ctx,ierr)
221: implicit none
222: #include include/finclude/petsc.h
223: #include include/finclude/petscvec.h
224: #include include/finclude/petscda.h
225: #include include/finclude/petscmat.h
226: #include include/finclude/petscsnes.h
227: SNES snes
228: Vec x
229: Mat jac,B
230: PetscFortranAddr ctx(*)
231: integer flag,ii,istart
232: PetscOffset ixx
233: integer iend,i,j,n,rank,size,end,start,ierr
234: PetscScalar d,A,h,vxx(1)
237: h = 1.d0/(ctx(6) - 1.d0)
238: d = h*h
239: rank = ctx(4)
240: size = ctx(5)
242: call VecGetArray(x,vxx,ixx,ierr)
243: call VecGetOwnershipRange(x,start,end,ierr)
244: n = end - start
246: if (rank .eq. 0) then
247: A = 1.0
248: call MatSetValues(jac,1,start,1,start,A,INSERT_VALUES,ierr)
249: istart = 1
250: else
251: istart = 0
252: endif
253: if (rank .eq. size-1) then
254: i = ctx(6)-1
255: A = 1.0
256: call MatSetValues(jac,1,i,1,i,A,INSERT_VALUES,ierr)
257: iend = n-1
258: else
259: iend = n
260: endif
261: do 10 i=istart,iend-1
262: ii = i + start
263: j = start + i - 1
264: call MatSetValues(jac,1,ii,1,j,d,INSERT_VALUES,ierr)
265: j = start + i + 1
266: call MatSetValues(jac,1,ii,1,j,d,INSERT_VALUES,ierr)
267: A = -2.0*d + 2.0*xx(i+1)
268: call MatSetValues(jac,1,ii,1,ii,A,INSERT_VALUES,ierr)
269: 10 continue
270: call VecRestoreArray(x,vxx,ixx,ierr)
271: call MatAssemblyBegin(jac,MAT_FINAL_ASSEMBLY,ierr)
272: call MatAssemblyEnd(jac,MAT_FINAL_ASSEMBLY,ierr)
273: return
274: end