xref: /petsc/src/dm/tutorials/ex5.c (revision 4e278199b78715991f5c71ebbd945c1489263e6c)
1 
2 static char help[] = "Tests DMDAGetElements() and VecView() contour plotting for 2d DMDAs.\n\n";
3 
4 #include <petscdm.h>
5 #include <petscdmda.h>
6 #include <petscdraw.h>
7 
8 int main(int argc,char **argv)
9 {
10   PetscInt         M = 10,N = 8,ne,nc,i;
11   const PetscInt   *e;
12   PetscErrorCode   ierr;
13   PetscBool        flg = PETSC_FALSE;
14   DM               da;
15   PetscViewer      viewer;
16   Vec              local,global;
17   PetscScalar      value;
18   DMBoundaryType   bx    = DM_BOUNDARY_NONE,by = DM_BOUNDARY_NONE;
19   DMDAStencilType  stype = DMDA_STENCIL_BOX;
20   PetscScalar      *lv;
21 
22   ierr = PetscInitialize(&argc,&argv,(char*)0,help);if (ierr) return ierr;
23   ierr = PetscViewerDrawOpen(PETSC_COMM_WORLD,0,"",300,0,300,300,&viewer);CHKERRQ(ierr);
24 
25   /* Read options */
26   ierr = PetscOptionsGetInt(NULL,NULL,"-M",&M,NULL);CHKERRQ(ierr);
27   ierr = PetscOptionsGetInt(NULL,NULL,"-N",&N,NULL);CHKERRQ(ierr);
28   ierr = PetscOptionsGetBool(NULL,NULL,"-star_stencil",&flg,NULL);CHKERRQ(ierr);
29   if (flg) stype = DMDA_STENCIL_STAR;
30 
31   /* Create distributed array and get vectors */
32   ierr = DMDACreate2d(PETSC_COMM_WORLD,bx,by,stype,M,N,PETSC_DECIDE,PETSC_DECIDE,1,1,NULL,NULL,&da);CHKERRQ(ierr);
33   ierr = DMSetFromOptions(da);CHKERRQ(ierr);
34   ierr = DMSetUp(da);CHKERRQ(ierr);
35   ierr = DMCreateGlobalVector(da,&global);CHKERRQ(ierr);
36   ierr = DMCreateLocalVector(da,&local);CHKERRQ(ierr);
37 
38   value = -3.0;
39   ierr  = VecSet(global,value);CHKERRQ(ierr);
40   ierr  = DMGlobalToLocalBegin(da,global,INSERT_VALUES,local);CHKERRQ(ierr);
41   ierr  = DMGlobalToLocalEnd(da,global,INSERT_VALUES,local);CHKERRQ(ierr);
42 
43   ierr = DMDASetElementType(da,DMDA_ELEMENT_P1);CHKERRQ(ierr);
44   ierr = DMDAGetElements(da,&ne,&nc,&e);CHKERRQ(ierr);
45   ierr = VecGetArray(local,&lv);CHKERRQ(ierr);
46   for (i=0; i<ne; i++) {
47     ierr       = PetscSynchronizedPrintf(PETSC_COMM_WORLD,"i %D e[3*i] %D %D %D\n",i,e[3*i],e[3*i+1],e[3*i+2]);CHKERRQ(ierr);
48     lv[e[3*i]] = i;
49   }
50   ierr = PetscSynchronizedFlush(PETSC_COMM_WORLD,stdout);CHKERRQ(ierr);
51   ierr = VecRestoreArray(local,&lv);CHKERRQ(ierr);
52   ierr = DMDARestoreElements(da,&ne,&nc,&e);CHKERRQ(ierr);
53 
54   ierr = DMLocalToGlobalBegin(da,local,ADD_VALUES,global);CHKERRQ(ierr);
55   ierr = DMLocalToGlobalEnd(da,local,ADD_VALUES,global);CHKERRQ(ierr);
56 
57   ierr = DMView(da,viewer);CHKERRQ(ierr);
58   ierr = VecView(global,viewer);CHKERRQ(ierr);
59 
60   /* Free memory */
61   ierr = PetscViewerDestroy(&viewer);CHKERRQ(ierr);
62   ierr = VecDestroy(&local);CHKERRQ(ierr);
63   ierr = VecDestroy(&global);CHKERRQ(ierr);
64   ierr = DMDestroy(&da);CHKERRQ(ierr);
65   ierr = PetscFinalize();
66   return ierr;
67 }
68 
69 /*TEST
70 
71    test:
72      requires: x
73 
74    test:
75      suffix: 2
76      nsize: 2
77      requires: x
78 
79 TEST*/
80