Actual source code: ex3.c
1: /*$Id: ex3.c,v 1.49 2001/08/07 21:31:49 bsmith Exp $*/
3: static char help[] = "Solves the 1-dimensional wave equation.nn";
5: #include petscda.h
6: #include petscsys.h
8: int main(int argc,char **argv)
9: {
10: int rank,size,M = 60,ierr, time_steps = 100;
11: int localsize,j,i,mybase,myend,width,xbase,*localnodes = PETSC_NULL;
12: DA da;
13: PetscViewer viewer,viewer_private;
14: PetscDraw draw;
15: Vec local,global,copy;
16: PetscScalar *localptr,*copyptr;
17: PetscReal a,h,k;
18: PetscTruth flg;
19:
20: PetscInitialize(&argc,&argv,(char*)0,help);
21: MPI_Comm_rank(PETSC_COMM_WORLD,&rank);
22: MPI_Comm_size(PETSC_COMM_WORLD,&size);
24: PetscOptionsGetInt(PETSC_NULL,"-M",&M,PETSC_NULL);
25: PetscOptionsGetInt(PETSC_NULL,"-time",&time_steps,PETSC_NULL);
26: /*
27: Test putting two nodes on each processor, exact last processor gets the rest
28: */
29: PetscOptionsHasName(PETSC_NULL,"-distribute",&flg);
30: if (flg) {
31: PetscMalloc(size*sizeof(int),&localnodes);
32: for (i=0; i<size-1; i++) { localnodes[i] = 2;}
33: localnodes[size-1] = M - 2*(size-1);
34: }
35:
36: /* Set up the array */
37: DACreate1d(PETSC_COMM_WORLD,DA_XPERIODIC,M,1,1,localnodes,&da);
38: if (localnodes) {PetscFree(localnodes);}
39: DACreateGlobalVector(da,&global);
40: DACreateLocalVector(da,&local);
42: /* Set up display to show combined wave graph */
43: PetscViewerDrawOpen(PETSC_COMM_WORLD,0,"Entire Solution",20,480,800,200,&viewer);
44: PetscViewerDrawGetDraw(viewer,0,&draw);
45: PetscDrawSetDoubleBuffer(draw);
47: /* determine starting point of each processor */
48: VecGetOwnershipRange(global,&mybase,&myend);
50: /* set up display to show my portion of the wave */
51: xbase = (int)((mybase)*((800.0 - 4.0*size)/M) + 4.0*rank);
52: width = (int)((myend-mybase)*800./M);
53: PetscViewerDrawOpen(PETSC_COMM_SELF,0,"Local Portion of Solution",xbase,200,
54: width,200,&viewer_private);
55: PetscViewerDrawGetDraw(viewer_private,0,&draw);
56: PetscDrawSetDoubleBuffer(draw);
60: /* Initialize the array */
61: VecGetLocalSize(local,&localsize);
62: VecGetArray(local,&localptr);
63: localptr[0] = 0.0;
64: localptr[localsize-1] = 0.0;
65: for (i=1; i<localsize-1; i++) {
66: j=(i-1)+mybase;
67: localptr[i] = sin((PETSC_PI*j*6)/((PetscReal)M)
68: + 1.2 * sin((PETSC_PI*j*2)/((PetscReal)M))) * 2;
69: }
71: VecRestoreArray(local,&localptr);
72: DALocalToGlobal(da,local,INSERT_VALUES,global);
74: /* Make copy of local array for doing updates */
75: VecDuplicate(local,©);
77: /* Assign Parameters */
78: a= 1.0;
79: h= 1.0/M;
80: k= h;
82: for (j=0; j<time_steps; j++) {
84: /* Global to Local */
85: DAGlobalToLocalBegin(da,global,INSERT_VALUES,local);
86: DAGlobalToLocalEnd(da,global,INSERT_VALUES,local);
88: /*Extract local array */
89: VecGetArray(local,&localptr);
90: VecGetArray(copy,©ptr);
92: /* Update Locally - Make array of new values */
93: /* Note: I don't do anything for the first and last entry */
94: for (i=1; i< localsize-1; i++) {
95: copyptr[i] = .5*(localptr[i+1]+localptr[i-1]) -
96: (k / (2.0*a*h)) * (localptr[i+1] - localptr[i-1]);
97: }
98: VecRestoreArray(copy,©ptr);
99: VecRestoreArray(local,&localptr);
101: /* Local to Global */
102: DALocalToGlobal(da,copy,INSERT_VALUES,global);
103:
104: /* View my part of Wave */
105: VecView(copy,viewer_private);
107: /* View global Wave */
108: VecView(global,viewer);
109: }
111: DADestroy(da);
112: PetscViewerDestroy(viewer);
113: PetscViewerDestroy(viewer_private);
114: VecDestroy(copy);
115: VecDestroy(local);
116: VecDestroy(global);
118: PetscFinalize();
119: return 0;
120: }
121: