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.\n\n";
5: #include petscda.h
6: #include petscsys.h
10: int main(int argc,char **argv)
11: {
12: int rank,size,M = 60,ierr, time_steps = 100;
13: int localsize,j,i,mybase,myend,width,xbase,*localnodes = PETSC_NULL;
14: DA da;
15: PetscViewer viewer,viewer_private;
16: PetscDraw draw;
17: Vec local,global,copy;
18: PetscScalar *localptr,*copyptr;
19: PetscReal a,h,k;
20: PetscTruth flg;
21:
22: PetscInitialize(&argc,&argv,(char*)0,help);
23: MPI_Comm_rank(PETSC_COMM_WORLD,&rank);
24: MPI_Comm_size(PETSC_COMM_WORLD,&size);
26: PetscOptionsGetInt(PETSC_NULL,"-M",&M,PETSC_NULL);
27: PetscOptionsGetInt(PETSC_NULL,"-time",&time_steps,PETSC_NULL);
28: /*
29: Test putting two nodes on each processor, exact last processor gets the rest
30: */
31: PetscOptionsHasName(PETSC_NULL,"-distribute",&flg);
32: if (flg) {
33: PetscMalloc(size*sizeof(int),&localnodes);
34: for (i=0; i<size-1; i++) { localnodes[i] = 2;}
35: localnodes[size-1] = M - 2*(size-1);
36: }
37:
38: /* Set up the array */
39: DACreate1d(PETSC_COMM_WORLD,DA_XPERIODIC,M,1,1,localnodes,&da);
40: if (localnodes) {PetscFree(localnodes);}
41: DACreateGlobalVector(da,&global);
42: DACreateLocalVector(da,&local);
44: /* Set up display to show combined wave graph */
45: PetscViewerDrawOpen(PETSC_COMM_WORLD,0,"Entire Solution",20,480,800,200,&viewer);
46: PetscViewerDrawGetDraw(viewer,0,&draw);
47: PetscDrawSetDoubleBuffer(draw);
49: /* determine starting point of each processor */
50: VecGetOwnershipRange(global,&mybase,&myend);
52: /* set up display to show my portion of the wave */
53: xbase = (int)((mybase)*((800.0 - 4.0*size)/M) + 4.0*rank);
54: width = (int)((myend-mybase)*800./M);
55: PetscViewerDrawOpen(PETSC_COMM_SELF,0,"Local Portion of Solution",xbase,200,
56: width,200,&viewer_private);
57: PetscViewerDrawGetDraw(viewer_private,0,&draw);
58: PetscDrawSetDoubleBuffer(draw);
62: /* Initialize the array */
63: VecGetLocalSize(local,&localsize);
64: VecGetArray(local,&localptr);
65: localptr[0] = 0.0;
66: localptr[localsize-1] = 0.0;
67: for (i=1; i<localsize-1; i++) {
68: j=(i-1)+mybase;
69: localptr[i] = sin((PETSC_PI*j*6)/((PetscReal)M)
70: + 1.2 * sin((PETSC_PI*j*2)/((PetscReal)M))) * 2;
71: }
73: VecRestoreArray(local,&localptr);
74: DALocalToGlobal(da,local,INSERT_VALUES,global);
76: /* Make copy of local array for doing updates */
77: VecDuplicate(local,©);
79: /* Assign Parameters */
80: a= 1.0;
81: h= 1.0/M;
82: k= h;
84: for (j=0; j<time_steps; j++) {
86: /* Global to Local */
87: DAGlobalToLocalBegin(da,global,INSERT_VALUES,local);
88: DAGlobalToLocalEnd(da,global,INSERT_VALUES,local);
90: /*Extract local array */
91: VecGetArray(local,&localptr);
92: VecGetArray(copy,©ptr);
94: /* Update Locally - Make array of new values */
95: /* Note: I don't do anything for the first and last entry */
96: for (i=1; i< localsize-1; i++) {
97: copyptr[i] = .5*(localptr[i+1]+localptr[i-1]) -
98: (k / (2.0*a*h)) * (localptr[i+1] - localptr[i-1]);
99: }
100: VecRestoreArray(copy,©ptr);
101: VecRestoreArray(local,&localptr);
103: /* Local to Global */
104: DALocalToGlobal(da,copy,INSERT_VALUES,global);
105:
106: /* View my part of Wave */
107: VecView(copy,viewer_private);
109: /* View global Wave */
110: VecView(global,viewer);
111: }
113: DADestroy(da);
114: PetscViewerDestroy(viewer);
115: PetscViewerDestroy(viewer_private);
116: VecDestroy(copy);
117: VecDestroy(local);
118: VecDestroy(global);
120: PetscFinalize();
121: return 0;
122: }
123: