Actual source code: ex16.F
1: !
2: ! "$Id: ex16.F,v 1.29 2001/08/07 03:03:57 balay Exp $";
3: !
4: program main
5: implicit none
7: #include include/finclude/petsc.h
8: #include include/finclude/petscvec.h
9: #include include/finclude/petscmat.h
10: #include include/finclude/petscpc.h
11: #include include/finclude/petscsles.h
12: #include include/finclude/petscviewer.h
13: #include include/finclude/petscis.h
14: !
15: ! This example is a modified Fortran version of ex6.c. It tests the use of
16: ! options prefixes in PETSc. Two linear problems are solved in this program.
17: ! The first problem is read from a file. The second problem is constructed
18: ! from the first, by eliminating some of the entries of the linear matrix 'A'.
20: ! Each solve is distinguished by a unique prefix - 'a' for the first, 'b'
21: ! for the second. With the prefix the user can distinguish between the various
22: ! options (command line, from .petscrc file, etc.) for each of the solvers.
23: ! Input arguments are:
24: ! -f <input_file> : file to load. For a 5X5 example of the 5-pt. stencil
25: ! use the file petsc/src/mat/examples/mat.ex.binary
27: integer ierr,its,flg
28: PetscScalar norm,none,five
29: Vec x,b,u
30: Mat A
31: SLES sles1,sles2
32: character*(128) f
33: PetscViewer fd
34: IS isrow
35: PetscLogDouble time1,time2
37: none = -1.0
38: five = 5.0
39: call PetscInitialize(PETSC_NULL_CHARACTER,ierr)
41: ! Read in matrix and RHS
42: call PetscOptionsGetString(PETSC_NULL_CHARACTER,'-f',f,flg,ierr)
43: call PetscViewerBinaryOpen(PETSC_COMM_WORLD,f,PETSC_BINARY_RDONLY, &
44: & fd,ierr)
45: if (ierr .ne. 0) then
46: print*, 'Unable to open file ',f
47: SETERRQ(1,' ',ierr)
48: endif
50: call MatLoad(fd,MATSEQAIJ,A,ierr)
51: if (ierr .ne. 0) then
52: print*, 'Unable to load matrix '
53: SETERRQ(1,' ',ierr)
54: endif
56: call VecLoad(fd,b,ierr)
57: call PetscViewerDestroy(fd,ierr)
59: ! Set up solution
60: call VecDuplicate(b,x,ierr)
61: call VecDuplicate(b,u,ierr)
63: ! Solve system-1
64: call SLESCreate(PETSC_COMM_WORLD,sles1,ierr)
65: call SLESSetOptionsPrefix(sles1,'a',ierr)
66: call SLESAppendOptionsPrefix(sles1,'_',ierr)
67: call SLESSetOperators(sles1,A,A,DIFFERENT_NONZERO_PATTERN, &
68: & ierr)
69: call SLESSetFromOptions(sles1,ierr)
70: call PetscGetTime(time1,ierr)
71: call SLESSolve(sles1,b,x,its,ierr)
72: call PetscGetTime(time2,ierr)
74: ! Show result
75: call MatMult(A,x,u,ierr)
76: call VecAXPY(none,b,u,ierr)
77: call VecNorm(u,NORM_2,norm,ierr)
79: ! print*, 'Time for solve = ',time2-time1
81: write(6,100) norm,its
82: 100 format('Residual norm ',e10.4,' iterations ',i5)
84: ! Create system 2 by striping off some rows of the matrix
85: call ISCreateStride(PETSC_COMM_SELF,5,0,1,isrow,ierr)
86: call MatZeroRows(A,isrow,five,ierr)
88: ! Solve system-2
89: call SLESCreate(PETSC_COMM_WORLD,sles2,ierr)
90: call SLESSetOptionsPrefix(sles2,'b',ierr)
91: call SLESAppendOptionsPrefix(sles2,'_',ierr)
92: call SLESSetOperators(sles2,A,A,DIFFERENT_NONZERO_PATTERN, &
93: & ierr)
94: call SLESSetFromOptions(sles2,ierr)
95: call PetscGetTime(time1,ierr)
96: call SLESSolve(sles2,b,x,its,ierr)
97: call PetscGetTime(time2,ierr)
99: ! Show result
100: call MatMult(A,x,u,ierr)
101: call VecAXPY(none,b,u,ierr)
102: call VecNorm(u,NORM_2,norm,ierr)
103: ! print*, 'Time for solve = ',time2-time1
104: write(6,100) norm,its
106: ! Cleanup
107: call SLESDestroy(sles1,ierr)
108: call SLESDestroy(sles2,ierr)
109: call VecDestroy(b,ierr)
110: call VecDestroy(x,ierr)
111: call VecDestroy(u,ierr)
112: call MatDestroy(A,ierr)
113: call ISDestroy(isrow,ierr)
115: call PetscFinalize(ierr)
116: end