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

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

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

 23:   PetscInitialize(&argc,&argv,(char*)0,help);
 24:   MPI_Comm_rank(PETSC_COMM_WORLD,&rank);
 25:   MPI_Comm_size(PETSC_COMM_WORLD,&size);

 27:   PetscOptionsGetInt(NULL,"-M",&M,NULL);
 28:   PetscOptionsGetInt(NULL,"-time",&time_steps,NULL);
 29:   /*
 30:       Test putting two nodes on each processor, exact last processor gets the rest
 31:   */
 32:   PetscOptionsGetBool(NULL,"-distribute",&flg,NULL);
 33:   if (flg) {
 34:     PetscMalloc1(size,&localnodes);
 35:     for (i=0; i<size-1; i++) localnodes[i] = 2;
 36:     localnodes[size-1] = M - 2*(size-1);
 37:   }

 39:   /* Set up the array */
 40:   DMDACreate1d(PETSC_COMM_WORLD,DM_BOUNDARY_PERIODIC,M,1,1,localnodes,&da);
 41:   PetscFree(localnodes);
 42:   DMCreateGlobalVector(da,&global);
 43:   DMCreateLocalVector(da,&local);

 45:   /* Set up display to show combined wave graph */
 46:   PetscViewerDrawOpen(PETSC_COMM_WORLD,0,"Entire Solution",20,480,800,200,&viewer);
 47:   PetscViewerDrawGetDraw(viewer,0,&draw);
 48:   PetscDrawSetDoubleBuffer(draw);

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

 53:   /* set up display to show my portion of the wave */
 54:   xbase = (int)((mybase)*((800.0 - 4.0*size)/M) + 4.0*rank);
 55:   width = (int)((myend-mybase)*800./M);
 56:   PetscViewerDrawOpen(PETSC_COMM_SELF,0,"Local Portion of Solution",xbase,200,
 57:                               width,200,&viewer_private);
 58:   PetscViewerDrawGetDraw(viewer_private,0,&draw);
 59:   PetscDrawSetDoubleBuffer(draw);



 63:   /* Initialize the array */
 64:   VecGetLocalSize(local,&localsize);
 65:   VecGetArray(local,&localptr);

 67:   localptr[0] = 0.0;
 68:   localptr[localsize-1] = 0.0;
 69:   for (i=1; i<localsize-1; i++) {
 70:     j           = (i-1)+mybase;
 71:     localptr[i] = PetscSinReal((PETSC_PI*j*6)/((PetscReal)M) + 1.2 * PetscSinReal((PETSC_PI*j*2)/((PetscReal)M))) * 2;
 72:   }

 74:   VecRestoreArray(local,&localptr);
 75:   DMLocalToGlobalBegin(da,local,INSERT_VALUES,global);
 76:   DMLocalToGlobalEnd(da,local,INSERT_VALUES,global);

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

 81:   /* Assign Parameters */
 82:   a= 1.0;
 83:   h= 1.0/M;
 84:   k= h;

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

 88:     /* Global to Local */
 89:     DMGlobalToLocalBegin(da,global,INSERT_VALUES,local);
 90:     DMGlobalToLocalEnd(da,global,INSERT_VALUES,local);

 92:     /*Extract local array */
 93:     VecGetArray(local,&localptr);
 94:     VecGetArray(copy,&copyptr);

 96:     /* Update Locally - Make array of new values */
 97:     /* Note: I don't do anything for the first and last entry */
 98:     for (i=1; i< localsize-1; i++) {
 99:       copyptr[i] = .5*(localptr[i+1]+localptr[i-1]) - (k / (2.0*a*h)) * (localptr[i+1] - localptr[i-1]);
100:     }
101:     VecRestoreArray(copy,&copyptr);
102:     VecRestoreArray(local,&localptr);

104:     /* Local to Global */
105:     DMLocalToGlobalBegin(da,copy,INSERT_VALUES,global);
106:     DMLocalToGlobalEnd(da,copy,INSERT_VALUES,global);

108:     /* View my part of Wave */
109:     VecView(copy,viewer_private);

111:     /* View global Wave */
112:     VecView(global,viewer);
113:   }

115:   DMDestroy(&da);
116:   PetscViewerDestroy(&viewer);
117:   PetscViewerDestroy(&viewer_private);
118:   VecDestroy(&copy);
119:   VecDestroy(&local);
120:   VecDestroy(&global);

122:   PetscFinalize();
123:   return 0;
124: }