Actual source code: ex1.c

  2: static char help[] = "Tests VecView() contour plotting for 2d DAs.\n\n";

  4: /* 
  5:   MATLAB must be installed to configure PETSc to have MATLAB engine.
  6: Unless you have specific important reasons for using the Matlab engine, we do not
  7: recommend it. If you want to use Matlab for visualization and maybe a little post processing
  8: then you can use the socket viewer and send the data to Matlab via that.

 10:   VecView() on DA vectors first puts the Vec elements into global natural ordering before printing (or plotting)
 11: them. In 2d 5 by 2 DA this means the numbering is

 13:      5  6   7   8   9
 14:      0  1   2   3   4

 16: Now the default split across 2 processors with the DA  is (by rank)

 18:     0  0   0  1   1
 19:     0  0   0  1   1

 21: So the global PETSc ordering is

 23:     3  4  5   8  9
 24:     0  1  2   6  7

 26: Use the options
 27:      -da_grid_x <nx> - number of grid points in x direction, if M < 0
 28:      -da_grid_y <ny> - number of grid points in y direction, if N < 0
 29:      -da_processors_x <MX> number of processors in x directio
 30:      -da_processors_y <MY> number of processors in x direction
 31: */

 33:  #include petscda.h

 37: int main(int argc,char **argv)
 38: {
 39:   PetscMPIInt    rank;
 40:   PetscInt       M = -10,N = -8;
 42:   PetscTruth     flg = PETSC_FALSE;
 43:   DA             da;
 44:   PetscViewer    viewer;
 45:   Vec            local,global;
 46:   PetscScalar    value;
 47:   DAPeriodicType ptype = DA_NONPERIODIC;
 48:   DAStencilType  stype = DA_STENCIL_BOX;
 49: #if defined(PETSC_HAVE_MATLAB_ENGINE)
 50:   PetscViewer    mviewer;
 51: #endif

 53:   PetscInitialize(&argc,&argv,(char*)0,help);
 54:   PetscViewerDrawOpen(PETSC_COMM_WORLD,0,"",300,0,300,300,&viewer);
 55: #if defined(PETSC_HAVE_MATLAB_ENGINE)
 56:   PetscViewerMatlabOpen(PETSC_COMM_WORLD,"tmp.mat",FILE_MODE_WRITE,&mviewer);
 57: #endif

 59:   PetscOptionsGetTruth(PETSC_NULL,"-star_stencil",&flg,PETSC_NULL);
 60:   if (flg) stype = DA_STENCIL_STAR;
 61: 
 62:   /* Create distributed array and get vectors */
 63:   DACreate2d(PETSC_COMM_WORLD,ptype,stype,M,N,PETSC_DECIDE,PETSC_DECIDE,1,1,PETSC_NULL,PETSC_NULL,&da);
 64:   DACreateGlobalVector(da,&global);
 65:   DACreateLocalVector(da,&local);

 67:   value = -3.0;
 68:   VecSet(global,value);
 69:   DAGlobalToLocalBegin(da,global,INSERT_VALUES,local);
 70:   DAGlobalToLocalEnd(da,global,INSERT_VALUES,local);

 72:   MPI_Comm_rank(PETSC_COMM_WORLD,&rank);
 73:   value = rank+1;
 74:   VecScale(local,value);
 75:   DALocalToGlobal(da,local,ADD_VALUES,global);
 76: 
 77:   flg  = PETSC_FALSE;
 78:   PetscOptionsGetTruth(PETSC_NULL, "-view_global", &flg,PETSC_NULL);
 79:   if (flg) { /* view global vector in natural ordering */
 80:     VecView(global,PETSC_VIEWER_STDOUT_WORLD);
 81:   }
 82:   DAView(da,viewer);
 83:   VecView(global,viewer);
 84: #if defined(PETSC_HAVE_MATLAB_ENGINE)
 85:   DAView(da,mviewer);
 86:   VecView(global,mviewer);
 87: #endif

 89:   /* Free memory */
 90: #if defined(PETSC_HAVE_MATLAB_ENGINE)
 91:   PetscViewerDestroy(mviewer);
 92: #endif
 93:   PetscViewerDestroy(viewer);
 94:   VecDestroy(local);
 95:   VecDestroy(global);
 96:   DADestroy(da);
 97:   PetscFinalize();
 98:   return 0;
 99: }
100: