Actual source code: ex21.c
petsc-3.7.1 2016-05-15
1: static const char help[] = "Tests MatGetSchurComplement\n";
3: #include <petscksp.h>
8: PetscErrorCode Create(MPI_Comm comm,Mat *inA,IS *is0,IS *is1)
9: {
11: Mat A;
12: PetscInt r,rend,M;
13: PetscMPIInt rank;
16: *inA = 0;
17: MatCreate(comm,&A);
18: MatSetSizes(A,4,4,PETSC_DETERMINE,PETSC_DETERMINE);
19: MatSetFromOptions(A);
20: MatSetUp(A);
21: MatGetOwnershipRange(A,&r,&rend);
22: MatGetSize(A,&M,NULL);
24: ISCreateStride(comm,2,r,1,is0);
25: ISCreateStride(comm,2,r+2,1,is1);
27: MPI_Comm_rank(comm,&rank);
29: {
30: PetscInt rows[4],cols0[5],cols1[5],cols2[3],cols3[3];
31: PetscScalar RR = 1000.*rank,vals0[5],vals1[4],vals2[3],vals3[3];
33: rows[0] = r;
34: rows[1] = r+1;
35: rows[2] = r+2;
36: rows[3] = r+3;
38: cols0[0] = r+0;
39: cols0[1] = r+1;
40: cols0[2] = r+3;
41: cols0[3] = (r+4)%M;
42: cols0[4] = (r+M-4)%M;
44: cols1[0] = r+1;
45: cols1[1] = r+2;
46: cols1[2] = (r+4+1)%M;
47: cols1[3] = (r+M-4+1)%M;
49: cols2[0] = r;
50: cols2[1] = r+2;
51: cols2[2] = (r+4+2)%M;
53: cols3[0] = r+1;
54: cols3[1] = r+3;
55: cols3[2] = (r+4+3)%M;
57: vals0[0] = RR+1.;
58: vals0[1] = RR+2.;
59: vals0[2] = RR+3.;
60: vals0[3] = RR+4.;
61: vals0[4] = RR+5.;
63: vals1[0] = RR+6.;
64: vals1[1] = RR+7.;
65: vals1[2] = RR+8.;
66: vals1[3] = RR+9.;
68: vals2[0] = RR+10.;
69: vals2[1] = RR+11.;
70: vals2[2] = RR+12.;
72: vals3[0] = RR+13.;
73: vals3[1] = RR+14.;
74: vals3[2] = RR+15.;
75: MatSetValues(A,1,&rows[0],5,cols0,vals0,INSERT_VALUES);
76: MatSetValues(A,1,&rows[1],4,cols1,vals1,INSERT_VALUES);
77: MatSetValues(A,1,&rows[2],3,cols2,vals2,INSERT_VALUES);
78: MatSetValues(A,1,&rows[3],3,cols3,vals3,INSERT_VALUES);
79: }
80: MatAssemblyBegin(A,MAT_FINAL_ASSEMBLY);
81: MatAssemblyEnd (A,MAT_FINAL_ASSEMBLY);
82: *inA = A;
83: return(0);
84: }
88: PetscErrorCode Destroy(Mat *A,IS *is0,IS *is1)
89: {
93: MatDestroy(A);
94: ISDestroy(is0);
95: ISDestroy(is1);
96: return(0);
97: }
101: int main(int argc,char *argv[])
102: {
104: Mat A,S = NULL,Sexplicit = NULL;
105: IS is0,is1;
107: PetscInitialize(&argc,&argv,0,help);
110: /* Test the Schur complement one way */
111: Create(PETSC_COMM_WORLD,&A,&is0,&is1);
112: MatView(A,PETSC_VIEWER_STDOUT_WORLD);
113: ISView(is0,PETSC_VIEWER_STDOUT_WORLD);
114: ISView(is1,PETSC_VIEWER_STDOUT_WORLD);
115: MatGetSchurComplement(A,is0,is0,is1,is1,MAT_INITIAL_MATRIX,&S,MAT_SCHUR_COMPLEMENT_AINV_DIAG,MAT_IGNORE_MATRIX,NULL);
116: MatComputeExplicitOperator(S,&Sexplicit);
117: PetscPrintf(PETSC_COMM_WORLD,"\nExplicit Schur complement of (0,0) in (1,1)\n");
118: MatView(Sexplicit,PETSC_VIEWER_STDOUT_WORLD);
119: Destroy(&A,&is0,&is1);
120: MatDestroy(&S);
121: MatDestroy(&Sexplicit);
123: /* And the other */
124: Create(PETSC_COMM_WORLD,&A,&is0,&is1);
125: MatGetSchurComplement(A,is1,is1,is0,is0,MAT_INITIAL_MATRIX,&S,MAT_SCHUR_COMPLEMENT_AINV_DIAG,MAT_IGNORE_MATRIX,NULL);
126: MatComputeExplicitOperator(S,&Sexplicit);
127: PetscPrintf(PETSC_COMM_WORLD,"\nExplicit Schur complement of (1,1) in (0,0)\n");
128: MatView(Sexplicit,PETSC_VIEWER_STDOUT_WORLD);
129: Destroy(&A,&is0,&is1);
130: MatDestroy(&S);
131: MatDestroy(&Sexplicit);
133: /* This time just the preconditioning matrix. */
134: Create(PETSC_COMM_WORLD,&A,&is0,&is1);
135: MatGetSchurComplement(A,is0,is0,is1,is1,MAT_IGNORE_MATRIX,NULL,MAT_SCHUR_COMPLEMENT_AINV_DIAG,MAT_INITIAL_MATRIX,&S);
136: PetscPrintf(PETSC_COMM_WORLD,"\nPreconditioning Schur complement of (0,0) in (1,1)\n");
137: MatView(S,PETSC_VIEWER_STDOUT_WORLD);
138: /* Modify and refresh */
139: MatShift(A,1.);
140: MatGetSchurComplement(A,is0,is0,is1,is1,MAT_IGNORE_MATRIX,NULL,MAT_SCHUR_COMPLEMENT_AINV_DIAG,MAT_REUSE_MATRIX,&S);
141: PetscPrintf(PETSC_COMM_WORLD,"\nAfter update\n");
142: MatView(S,PETSC_VIEWER_STDOUT_WORLD);
143: Destroy(&A,&is0,&is1);
144: MatDestroy(&S);
146: PetscFinalize();
147: return 0;
148: }