Actual source code: ex27.c
1: /*$Id: ex27.c,v 1.20 2001/08/07 03:03:07 balay Exp $*/
3: static char help[] = "Tests repeated use of assembly for matrices.n
4: does nasty case where matrix must be rebuilt.nn";
6: #include petscmat.h
8: int main(int argc,char **args)
9: {
10: Mat C;
11: int i,j,m = 5,n = 2,I,J,ierr,rank,size;
12: PetscScalar v;
13: Vec x,y;
15: PetscInitialize(&argc,&args,(char *)0,help);
16: MPI_Comm_rank(PETSC_COMM_WORLD,&rank);
17: MPI_Comm_size(PETSC_COMM_WORLD,&size);
18: n = 2*size;
20: /* Create the matrix for the five point stencil, YET AGAIN */
21: MatCreate(PETSC_COMM_WORLD,PETSC_DECIDE,PETSC_DECIDE,m*n,m*n,&C);
22: MatSetFromOptions(C);
23: for (i=0; i<m; i++) {
24: for (j=2*rank; j<2*rank+2; j++) {
25: v = -1.0; I = j + n*i;
26: if (i>0) {J = I - n; MatSetValues(C,1,&I,1,&J,&v,INSERT_VALUES);}
27: if (i<m-1) {J = I + n; MatSetValues(C,1,&I,1,&J,&v,INSERT_VALUES);}
28: if (j>0) {J = I - 1; MatSetValues(C,1,&I,1,&J,&v,INSERT_VALUES);}
29: if (j<n-1) {J = I + 1; MatSetValues(C,1,&I,1,&J,&v,INSERT_VALUES);}
30: v = 4.0; MatSetValues(C,1,&I,1,&I,&v,INSERT_VALUES);
31: }
32: }
33: MatAssemblyBegin(C,MAT_FINAL_ASSEMBLY);
34: MatAssemblyEnd(C,MAT_FINAL_ASSEMBLY);
35: for (i=0; i<m; i++) {
36: for (j=2*rank; j<2*rank+2; j++) {
37: v = 1.0; I = j + n*i;
38: if (i>0) {J = I - n; MatSetValues(C,1,&I,1,&J,&v,INSERT_VALUES);}
39: if (i<m-1) {J = I + n; MatSetValues(C,1,&I,1,&J,&v,INSERT_VALUES);}
40: if (j>0) {J = I - 1; MatSetValues(C,1,&I,1,&J,&v,INSERT_VALUES);}
41: if (j<n-1) {J = I + 1; MatSetValues(C,1,&I,1,&J,&v,INSERT_VALUES);}
42: v = -4.0; MatSetValues(C,1,&I,1,&I,&v,INSERT_VALUES);
43: }
44: }
45: /* Introduce new nonzero that requires new construction for
46: matrix-vector product */
47: if (rank) {
48: I = rank-1; J = m*n-1;
49: MatSetValues(C,1,&I,1,&J,&v,INSERT_VALUES);
50: }
51: MatAssemblyBegin(C,MAT_FINAL_ASSEMBLY);
52: MatAssemblyEnd(C,MAT_FINAL_ASSEMBLY);
54: MatView(C,PETSC_VIEWER_STDOUT_WORLD);
56: /* Form a couple of vectors to test matrix-vector product */
57: VecCreate(PETSC_COMM_WORLD,&x);
58: VecSetSizes(x,PETSC_DECIDE,m*n);
59: VecSetFromOptions(x);
60: VecDuplicate(x,&y);
61: v = 1.0; VecSet(&v,x);
62: MatMult(C,x,y);
64: MatDestroy(C);
65: VecDestroy(x);
66: VecDestroy(y);
67: PetscFinalize();
68: return 0;
69: }