Actual source code: ex12.c

  1: /*$Id: ex12.c,v 1.41 2001/08/07 21:31:49 bsmith Exp $*/

  3: /*
  4:    Simple example to show how PETSc programs can be run from Matlab. 
  5:   See ex12.m.
  6: */

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

 10:  #include petscda.h
 11:  #include petscsys.h

 15: int main(int argc,char **argv)
 16: {
 17:   int         rank,size,M = 14,ierr,time_steps = 20,w=1,s=1;
 18:   DA          da;
 19:   PetscViewer viewer;
 20:   Vec         local,global,copy;
 21:   PetscScalar *localptr,*copyptr;
 22:   PetscReal   h,k;
 23:   int         localsize,j,i,mybase,myend;
 24: 
 25:   PetscInitialize(&argc,&argv,(char*)0,help);

 27:   PetscOptionsGetInt(PETSC_NULL,"-M",&M,PETSC_NULL);
 28:   PetscOptionsGetInt(PETSC_NULL,"-time",&time_steps,PETSC_NULL);
 29: 
 30:   /* Set up the array */
 31:   DACreate1d(PETSC_COMM_WORLD,DA_NONPERIODIC,M,w,s,PETSC_NULL,&da);
 32:   DACreateGlobalVector(da,&global);
 33:   DACreateLocalVector(da,&local);
 34:   MPI_Comm_rank(PETSC_COMM_WORLD,&rank);
 35:   MPI_Comm_size(PETSC_COMM_WORLD,&size);

 37:   /* Make copy of local array for doing updates */
 38:   VecDuplicate(local,&copy);
 39:   VecGetArray (copy,&copyptr);

 41:   /* Set Up Display to Show Heat Graph */
 42:   viewer = PETSC_VIEWER_SOCKET_WORLD;

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

 47:   /* Initialize the Array */
 48:   VecGetLocalSize (local,&localsize);
 49:   VecGetArray (local,&localptr);
 50:   localptr[0] = copyptr[0] = 0.0;
 51:   localptr[localsize-1] = copyptr[localsize-1] = 1.0;
 52:   for (i=1; i<localsize-1; i++) {
 53:     j=(i-1)+mybase;
 54:     localptr[i] = sin((PETSC_PI*j*6)/((PetscReal)M)
 55:                         + 1.2 * sin((PETSC_PI*j*2)/((PetscReal)M))) * 4+4;
 56:   }

 58:   VecRestoreArray (copy,&copyptr);
 59:   VecRestoreArray(local,&localptr);
 60:   DALocalToGlobal(da,local,INSERT_VALUES,global);

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

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

 68:     /* Global to Local */
 69:     DAGlobalToLocalBegin(da,global,INSERT_VALUES,local);
 70:     DAGlobalToLocalEnd(da,global,INSERT_VALUES,local);

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

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

 86:     /* Local to Global */
 87:     DALocalToGlobal(da,copy,INSERT_VALUES,global);
 88: 
 89:     /* View Wave */
 90:     VecView(global,viewer);

 92:   }

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