Actual source code: ex5.c

petsc-3.4.2 2013-07-02
  2: /* This file created by Peter Mell   6/30/95 */

  4: static char help[] = "Solves the one dimensional heat equation.\n\n";

  6: #include <petscdmda.h>
  7: #include <petscdraw.h>

 11: int main(int argc,char **argv)
 12: {
 13:   PetscMPIInt    rank,size;
 15:   PetscInt       M = 14,time_steps = 1000,w=1,s=1,localsize,j,i,mybase,myend;
 16:   DM             da;
 17:   PetscViewer    viewer;
 18:   PetscDraw      draw;
 19:   Vec            local,global,copy;
 20:   PetscScalar    *localptr,*copyptr;
 21:   PetscReal      h,k;

 23:   PetscInitialize(&argc,&argv,(char*)0,help);

 25:   PetscOptionsGetInt(NULL,"-M",&M,NULL);
 26:   PetscOptionsGetInt(NULL,"-time",&time_steps,NULL);

 28:   /* Set up the array */
 29:   DMDACreate1d(PETSC_COMM_WORLD,DMDA_BOUNDARY_NONE,M,w,s,NULL,&da);
 30:   DMCreateGlobalVector(da,&global);
 31:   DMCreateLocalVector(da,&local);
 32:   MPI_Comm_rank(PETSC_COMM_WORLD,&rank);
 33:   MPI_Comm_size(PETSC_COMM_WORLD,&size);

 35:   /* Make copy of local array for doing updates */
 36:   VecDuplicate(local,&copy);

 38:   /* Set Up Display to Show Heat Graph */
 39:   PetscViewerDrawOpen(PETSC_COMM_WORLD,0,"",80,480,500,160,&viewer);
 40:   PetscViewerDrawGetDraw(viewer,0,&draw);
 41:   PetscDrawSetDoubleBuffer(draw);

 43:   /* determine starting point of each processor */
 44:   VecGetOwnershipRange(global,&mybase,&myend);

 46:   /* Initialize the Array */
 47:   VecGetLocalSize (local,&localsize);
 48:   VecGetArray (local,&localptr);
 49:   VecGetArray (copy,&copyptr);

 51:   localptr[0] = copyptr[0] = 0.0;

 53:   localptr[localsize-1] = copyptr[localsize-1] = 1.0;
 54:   for (i=1; i<localsize-1; i++) {
 55:     j = (i-1) + mybase;

 57:     localptr[i] = sin((PETSC_PI*j*6)/((PetscReal)M) + 1.2 * sin((PETSC_PI*j*2)/((PetscReal)M))) * 4+4;
 58:   }

 60:   VecRestoreArray(local,&localptr);
 61:   VecRestoreArray(copy,&copyptr);
 62:   DMLocalToGlobalBegin(da,local,INSERT_VALUES,global);
 63:   DMLocalToGlobalEnd(da,local,INSERT_VALUES,global);

 65:   /* Assign Parameters */
 66:   h= 1.0/M;
 67:   k= h*h/2.2;

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

 71:     /* Global to Local */
 72:     DMGlobalToLocalBegin(da,global,INSERT_VALUES,local);
 73:     DMGlobalToLocalEnd(da,global,INSERT_VALUES,local);

 75:     /*Extract local array */
 76:     VecGetArray(local,&localptr);
 77:     VecGetArray (copy,&copyptr);

 79:     /* Update Locally - Make array of new values */
 80:     /* Note: I don't do anything for the first and last entry */
 81:     for (i=1; i< localsize-1; i++) {
 82:       copyptr[i] = localptr[i] + (k/(h*h)) * (localptr[i+1]-2.0*localptr[i]+localptr[i-1]);
 83:     }

 85:     VecRestoreArray(copy,&copyptr);
 86:     VecRestoreArray(local,&localptr);

 88:     /* Local to Global */
 89:     DMLocalToGlobalBegin(da,copy,INSERT_VALUES,global);
 90:     DMLocalToGlobalEnd(da,copy,INSERT_VALUES,global);

 92:     /* View Wave */
 93:     VecView(global,viewer);

 95:   }

 97:   PetscViewerDestroy(&viewer);
 98:   VecDestroy(&copy);
 99:   VecDestroy(&local);
100:   VecDestroy(&global);
101:   DMDestroy(&da);
102:   PetscFinalize();
103:   return 0;
104: }