Actual source code: ex6.c

      2: static char help[] = "Writes an array to a file, then reads an array from a file, then forms a vector.\n\n";

     4:  #include petscvec.h

      8: int main(int argc,char **args)
      9: {
     11:   PetscMPIInt    size;
     12:   int            fd;
     13:   PetscInt       i,m = 10,sz;
     14:   PetscScalar    *avec,*array;
     15:   Vec            vec;
     16:   PetscViewer    view_out,view_in;

     18:   PetscInitialize(&argc,&args,(char *)0,help);
     19:   MPI_Comm_size(PETSC_COMM_WORLD,&size);
     20:   if (size != 1) SETERRQ(1,"This is a uniprocessor example only!");
     21:
     22:   PetscOptionsGetInt(PETSC_NULL,"-m",&m,PETSC_NULL);

     24:   /* ---------------------------------------------------------------------- */
     25:   /*          PART 1: Write some data to a file in binary format            */
     26:   /* ---------------------------------------------------------------------- */

     28:   /* Allocate array and set values */
     29:   PetscMalloc(m*sizeof(PetscScalar),&array);
     30:   for (i=0; i<m; i++) {
     31:     array[i] = i*10.0;
     32:   }

     34:   /* Open viewer for binary output */
     35:   PetscViewerBinaryOpen(PETSC_COMM_SELF,"input.dat",PETSC_FILE_CREATE,&view_out);
     36:   PetscViewerBinaryGetDescriptor(view_out,&fd);

     38:   /* Write binary output */
     39:   PetscBinaryWrite(fd,&m,1,PETSC_INT,PETSC_FALSE);
     40:   PetscBinaryWrite(fd,array,m,PETSC_SCALAR,PETSC_FALSE);

     42:   /* Destroy the output viewer and work array */
     43:   PetscViewerDestroy(view_out);
     44:   PetscFree(array);

     46:   /* ---------------------------------------------------------------------- */
     47:   /*          PART 2: Read data from file and form a vector                 */
     48:   /* ---------------------------------------------------------------------- */

     50:   /* Open input binary viewer */
     51:   PetscViewerBinaryOpen(PETSC_COMM_SELF,"input.dat",PETSC_FILE_RDONLY,&view_in);
     52:   PetscViewerBinaryGetDescriptor(view_in,&fd);

     54:   /* Create vector and get pointer to data space */
     55:   VecCreate(PETSC_COMM_SELF,&vec);
     56:   VecSetSizes(vec,PETSC_DECIDE,m);
     57:   VecSetFromOptions(vec);
     58:   VecGetArray(vec,&avec);

     60:   /* Read data into vector */
     61:   PetscBinaryRead(fd,&sz,1,PETSC_INT);
     62:   if (sz <=0) SETERRQ(1,"Error: Must have array length > 0");

     64:   PetscPrintf(PETSC_COMM_SELF,"reading data in binary from input.dat, sz =%D ...\n",sz);
     65:   PetscBinaryRead(fd,avec,sz,PETSC_SCALAR);

     67:   /* View vector */
     68:   VecRestoreArray(vec,&avec);
     69:   VecView(vec,PETSC_VIEWER_STDOUT_SELF);

     71:   /* Free data structures */
     72:   VecDestroy(vec);
     73:   PetscViewerDestroy(view_in);
     74:   PetscFinalize();
     75:   return 0;
     76: }