2: /*
  3:    Simple example to show how PETSc programs can be run from MATLAB.
  4:   See ex12.m.
  5: */

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

  9: #include <petscdmda.h>

 13: int main(int argc,char **argv)
 14: {
 15:   PetscMPIInt    rank,size;
 16:   PetscInt       M = 14,time_steps = 20,w=1,s=1,localsize,j,i,mybase,myend;
 18:   DM             da;
 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);
 37:   VecGetArray (copy,&copyptr);


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

 43:   /* Initialize the Array */
 44:   VecGetLocalSize (local,&localsize);
 45:   VecGetArray (local,&localptr);

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

 49:   localptr[localsize-1] = copyptr[localsize-1] = 1.0;
 50:   for (i=1; i<localsize-1; i++) {
 51:     j = (i-1) + mybase;

 53:     localptr[i] = sin((PETSC_PI*j*6)/((PetscReal)M) + 1.2 * sin((PETSC_PI*j*2)/((PetscReal)M))) * 4+4;
 54:   }

 56:   VecRestoreArray (copy,&copyptr);
 57:   VecRestoreArray(local,&localptr);
 58:   DMLocalToGlobalBegin(da,local,INSERT_VALUES,global);
 59:   DMLocalToGlobalEnd(da,local,INSERT_VALUES,global);

 61:   /* Assign Parameters */
 62:   h= 1.0/M;
 63:   k= h*h/2.2;

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

 67:     /* Global to Local */
 68:     DMGlobalToLocalBegin(da,global,INSERT_VALUES,local);
 69:     DMGlobalToLocalEnd(da,global,INSERT_VALUES,local);

 71:     /*Extract local array */
 72:     VecGetArray(local,&localptr);
 73:     VecGetArray (copy,&copyptr);

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

 81:     VecRestoreArray (copy,&copyptr);
 82:     VecRestoreArray(local,&localptr);

 84:     /* Local to Global */
 85:     DMLocalToGlobalBegin(da,copy,INSERT_VALUES,global);
 86:     DMLocalToGlobalEnd(da,copy,INSERT_VALUES,global);

 88:     /* View Wave */
 89:     /* Set Up Display to Show Heat Graph */
 90: #if defined(PETSC_USE_SOCKET_VIEWER)
 91:     VecView(global,PETSC_VIEWER_SOCKET_WORLD);
 92: #endif
 93:   }

 95:   VecDestroy(&copy);
 96:   VecDestroy(&local);
 97:   VecDestroy(&global);
 98:   DMDestroy(&da);
 99:   PetscFinalize();
100:   return 0;
101: }