Actual source code: ex6.c
petsc-3.8.3 2017-12-09
2: static char help[] = "Creates a matrix using 9 pt stencil, and uses it to test MatIncreaseOverlap (needed for aditive schwarts preconditioner. \n\
3: -m <size> : problem size\n\
4: -x1, -x2 <size> : no of subdomains in x and y directions\n\n";
6: #include <petscksp.h>
8: PetscErrorCode FormElementStiffness(PetscReal H,PetscScalar *Ke)
9: {
10: Ke[0] = H/6.0; Ke[1] = -.125*H; Ke[2] = H/12.0; Ke[3] = -.125*H;
11: Ke[4] = -.125*H; Ke[5] = H/6.0; Ke[6] = -.125*H; Ke[7] = H/12.0;
12: Ke[8] = H/12.0; Ke[9] = -.125*H; Ke[10] = H/6.0; Ke[11] = -.125*H;
13: Ke[12] = -.125*H; Ke[13] = H/12.0; Ke[14] = -.125*H; Ke[15] = H/6.0;
14: return 0;
15: }
16: PetscErrorCode FormElementRhs(PetscReal x,PetscReal y,PetscReal H,PetscScalar *r)
17: {
18: r[0] = 0.; r[1] = 0.; r[2] = 0.; r[3] = 0.0;
19: return 0;
20: }
22: int main(int argc,char **args)
23: {
24: Mat C;
26: PetscInt i,m = 2,N,M,idx[4],Nsub1,Nsub2,ol=1,x1,x2;
27: PetscScalar Ke[16];
28: PetscReal x,y,h;
29: IS *is1,*is2;
30: PetscBool flg;
32: PetscInitialize(&argc,&args,(char*)0,help);if (ierr) return ierr;
33: PetscOptionsGetInt(NULL,NULL,"-m",&m,NULL);
34: N = (m+1)*(m+1); /* dimension of matrix */
35: M = m*m; /* number of elements */
36: h = 1.0/m; /* mesh width */
37: x1 = (m+1)/2;
38: x2 = x1;
39: PetscOptionsGetInt(NULL,NULL,"-x1",&x1,NULL);
40: PetscOptionsGetInt(NULL,NULL,"-x2",&x2,NULL);
41: /* create stiffness matrix */
42: MatCreateSeqAIJ(PETSC_COMM_SELF,N,N,9,NULL,&C);
44: /* forms the element stiffness for the Laplacian */
45: FormElementStiffness(h*h,Ke);
46: for (i=0; i<M; i++) {
47: /* location of lower left corner of element */
48: x = h*(i % m); y = h*(i/m);
49: /* node numbers for the four corners of element */
50: idx[0] = (m+1)*(i/m) + (i % m);
51: idx[1] = idx[0]+1; idx[2] = idx[1] + m + 1; idx[3] = idx[2] - 1;
52: MatSetValues(C,4,idx,4,idx,Ke,ADD_VALUES);
53: }
54: MatAssemblyBegin(C,MAT_FINAL_ASSEMBLY);
55: MatAssemblyEnd(C,MAT_FINAL_ASSEMBLY);
57: for (ol=0; ol<m+2; ++ol) {
59: PCASMCreateSubdomains2D(m+1,m+1,x1,x2,1,0,&Nsub1,&is1);
60: MatIncreaseOverlap(C,Nsub1,is1,ol);
61: PCASMCreateSubdomains2D(m+1,m+1,x1,x2,1,ol,&Nsub2,&is2);
63: PetscPrintf(PETSC_COMM_SELF,"flg == 1 => both index sets are same\n");
64: if (Nsub1 != Nsub2) {
65: PetscPrintf(PETSC_COMM_SELF,"Error: No of indes sets don't match\n");
66: }
68: for (i=0; i<Nsub1; ++i) {
69: ISEqual(is1[i],is2[i],&flg);
70: PetscPrintf(PETSC_COMM_SELF,"i = %D,flg = %d \n",i,(int)flg);
72: }
73: for (i=0; i<Nsub1; ++i) {ISDestroy(&&is1[i]);}
74: for (i=0; i<Nsub2; ++i) {ISDestroy(&&is2[i]);}
77: PetscFree(is1);
78: PetscFree(is2);
79: }
80: MatDestroy(&C);
81: PetscFinalize();
82: return ierr;
83: }