Actual source code: ex12.c


  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 <petscdm.h>
 10: #include <petscdmda.h>

 12: int main(int argc,char **argv)
 13: {
 14:   PetscMPIInt    rank,size;
 15:   PetscInt       M = 14,time_steps = 20,w=1,s=1,localsize,j,i,mybase,myend,globalsize;
 17:   DM             da;
 18:   Vec            global,local;
 19:   PetscScalar    *globalptr,*localptr;
 20:   PetscReal      h,k;

 22:   PetscInitialize(&argc,&argv,(char*)0,help);if (ierr) return ierr;
 23:   PetscOptionsGetInt(NULL,NULL,"-M",&M,NULL);
 24:   PetscOptionsGetInt(NULL,NULL,"-time",&time_steps,NULL);

 26:   /* Set up the array */
 27:   DMDACreate1d(PETSC_COMM_WORLD,DM_BOUNDARY_NONE,M,w,s,NULL,&da);
 28:   DMSetFromOptions(da);
 29:   DMSetUp(da);
 30:   DMCreateGlobalVector(da,&global);
 31:   MPI_Comm_rank(PETSC_COMM_WORLD,&rank);
 32:   MPI_Comm_size(PETSC_COMM_WORLD,&size);

 34:   /* Make copy of local array for doing updates */
 35:   DMCreateLocalVector(da,&local);

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

 40:   /* Initialize the Array */
 41:   VecGetLocalSize (global,&globalsize);
 42:   VecGetArray (global,&globalptr);

 44:   for (i=0; i<globalsize; i++) {
 45:     j = i + mybase;

 47:     globalptr[i] = PetscSinReal((PETSC_PI*j*6)/((PetscReal)M) + 1.2 * PetscSinReal((PETSC_PI*j*2)/((PetscReal)M))) * 4+4;
 48:   }

 50:   VecRestoreArray(global,&localptr);

 52:   /* Assign Parameters */
 53:   h= 1.0/M;
 54:   k= h*h/2.2;
 55:   VecGetLocalSize(local,&localsize);

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

 59:     /* Global to Local */
 60:     DMGlobalToLocalBegin(da,global,INSERT_VALUES,local);
 61:     DMGlobalToLocalEnd(da,global,INSERT_VALUES,local);

 63:     /*Extract local array */
 64:     VecGetArray(local,&localptr);
 65:     VecGetArray (global,&globalptr);

 67:     /* Update Locally - Make array of new values */
 68:     /* Note: I don't do anything for the first and last entry */
 69:     for (i=1; i< localsize-1; i++) {
 70:       globalptr[i-1] = localptr[i] + (k/(h*h)) * (localptr[i+1]-2.0*localptr[i]+localptr[i-1]);
 71:     }

 73:     VecRestoreArray (global,&globalptr);
 74:     VecRestoreArray(local,&localptr);

 76:     /* View Wave */
 77:     /* Set Up Display to Show Heat Graph */
 78: #if defined(PETSC_USE_SOCKET_VIEWER)
 79:     VecView(global,PETSC_VIEWER_SOCKET_WORLD);
 80: #endif
 81:   }

 83:   VecDestroy(&local);
 84:   VecDestroy(&global);
 85:   DMDestroy(&da);
 86:   PetscFinalize();
 87:   return ierr;
 88: }