Actual source code: ex3.c


  2: static char help[] = "Solves the 1-dimensional wave equation.\n\n";

  4: #include <petscdm.h>
  5: #include <petscdmda.h>
  6: #include <petscdraw.h>

  8: int main(int argc,char **argv)
  9: {
 10:   PetscMPIInt    rank,size;
 11:   PetscInt       M = 60,time_steps = 100, localsize,j,i,mybase,myend,width,xbase,*localnodes = NULL;
 12:   DM             da;
 13:   PetscViewer    viewer,viewer_private;
 14:   PetscDraw      draw;
 15:   Vec            local,global;
 16:   PetscScalar    *localptr,*globalptr;
 17:   PetscReal      a,h,k;
 18:   PetscBool      flg = PETSC_FALSE;

 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(NULL,NULL,"-M",&M,NULL);
 25:   PetscOptionsGetInt(NULL,NULL,"-time",&time_steps,NULL);
 26:   /*
 27:       Test putting two nodes on each processor, exact last processor gets the rest
 28:   */
 29:   PetscOptionsGetBool(NULL,NULL,"-distribute",&flg,NULL);
 30:   if (flg) {
 31:     PetscMalloc1(size,&localnodes);
 32:     for (i=0; i<size-1; i++) localnodes[i] = 2;
 33:     localnodes[size-1] = M - 2*(size-1);
 34:   }

 36:   /* Set up the array */
 37:   DMDACreate1d(PETSC_COMM_WORLD,DM_BOUNDARY_PERIODIC,M,1,1,localnodes,&da);
 38:   DMSetFromOptions(da);
 39:   DMSetUp(da);
 40:   PetscFree(localnodes);
 41:   DMCreateGlobalVector(da,&global);
 42:   DMCreateLocalVector(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,width,200,&viewer_private);
 56:   PetscViewerDrawGetDraw(viewer_private,0,&draw);
 57:   PetscDrawSetDoubleBuffer(draw);

 59:   /* Initialize the array */
 60:   VecGetLocalSize(local,&localsize);
 61:   VecGetArray(global,&globalptr);

 63:   for (i=1; i<localsize-1; i++) {
 64:     j           = (i-1)+mybase;
 65:     globalptr[i-1] = PetscSinReal((PETSC_PI*j*6)/((PetscReal)M) + 1.2 * PetscSinReal((PETSC_PI*j*2)/((PetscReal)M))) * 2;
 66:   }

 68:   VecRestoreArray(global,&globalptr);

 70:   /* Assign Parameters */
 71:   a= 1.0;
 72:   h= 1.0/M;
 73:   k= h;

 75:   for (j=0; j<time_steps; j++) {

 77:     /* Global to Local */
 78:     DMGlobalToLocalBegin(da,global,INSERT_VALUES,local);
 79:     DMGlobalToLocalEnd(da,global,INSERT_VALUES,local);

 81:     /*Extract local array */
 82:     VecGetArray(local,&localptr);
 83:     VecGetArray(global,&globalptr);

 85:     /* Update Locally - Make array of new values */
 86:     /* Note: I don't do anything for the first and last entry */
 87:     for (i=1; i< localsize-1; i++) {
 88:       globalptr[i-1] = .5*(localptr[i+1]+localptr[i-1]) - (k / (2.0*a*h)) * (localptr[i+1] - localptr[i-1]);
 89:     }
 90:     VecRestoreArray(global,&globalptr);
 91:     VecRestoreArray(local,&localptr);

 93:     /* View my part of Wave */
 94:     VecView(global,viewer_private);

 96:     /* View global Wave */
 97:     VecView(global,viewer);
 98:   }

100:   DMDestroy(&da);
101:   PetscViewerDestroy(&viewer);
102:   PetscViewerDestroy(&viewer_private);
103:   VecDestroy(&local);
104:   VecDestroy(&global);

106:   PetscFinalize();
107:   return 0;
108: }

110: /*TEST

112:     test:
113:       nsize: 3
114:       args: -time 50 -nox
115:       requires: x

117: TEST*/