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

  4: /*
  5:     This uses the low level PetscBinaryWrite() and PetscBinaryRead() to access a binary file. It will not work in parallel!

  7:     We HIGHLY recommend using instead VecView() and VecLoad() to read and write Vectors in binary format (which also work in parallel). Then you can use
  8:     share/petsc/matlab/PetscBinaryRead() and share/petsc/matlab/PetscBinaryWrite() to read (or write) the vector into MATLAB.

 10:     Note this also works for matrices with MatView() and MatLoad().
 11: */
 12: #include <petscvec.h>

 14: int main(int argc,char **args)
 15: {
 16:   PetscMPIInt    size;
 17:   int            fd;
 18:   PetscInt       i,m = 10,sz;
 19:   PetscScalar    *avec,*array;
 20:   Vec            vec;
 21:   PetscViewer    view_out,view_in;

 23:   PetscInitialize(&argc,&args,(char*)0,help);
 24:   MPI_Comm_size(PETSC_COMM_WORLD,&size);

 27:   PetscOptionsGetInt(NULL,NULL,"-m",&m,NULL);

 29:   /* ---------------------------------------------------------------------- */
 30:   /*          PART 1: Write some data to a file in binary format            */
 31:   /* ---------------------------------------------------------------------- */

 33:   /* Allocate array and set values */
 34:   PetscMalloc1(m,&array);
 35:   for (i=0; i<m; i++) array[i] = i*10.0;

 37:   /* Open viewer for binary output */
 38:   PetscViewerBinaryOpen(PETSC_COMM_SELF,"input.dat",FILE_MODE_WRITE,&view_out);
 39:   PetscViewerBinaryGetDescriptor(view_out,&fd);

 41:   /* Write binary output */
 42:   PetscBinaryWrite(fd,&m,1,PETSC_INT);
 43:   PetscBinaryWrite(fd,array,m,PETSC_SCALAR);

 45:   /* Destroy the output viewer and work array */
 46:   PetscViewerDestroy(&view_out);
 47:   PetscFree(array);

 49:   /* ---------------------------------------------------------------------- */
 50:   /*          PART 2: Read data from file and form a vector                 */
 51:   /* ---------------------------------------------------------------------- */

 53:   /* Open input binary viewer */
 54:   PetscViewerBinaryOpen(PETSC_COMM_SELF,"input.dat",FILE_MODE_READ,&view_in);
 55:   PetscViewerBinaryGetDescriptor(view_in,&fd);

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

 63:   /* Read data into vector */
 64:   PetscBinaryRead(fd,&sz,1,NULL,PETSC_INT);

 67:   PetscPrintf(PETSC_COMM_SELF,"reading data in binary from input.dat, sz =%" PetscInt_FMT " ...\n",sz);
 68:   PetscBinaryRead(fd,avec,sz,NULL,PETSC_SCALAR);

 70:   /* View vector */
 71:   VecRestoreArray(vec,&avec);
 72:   VecView(vec,PETSC_VIEWER_STDOUT_SELF);

 74:   /* Free data structures */
 75:   VecDestroy(&vec);
 76:   PetscViewerDestroy(&view_in);
 77:   PetscFinalize();
 78:   return 0;
 79: }

 81: /*TEST

 83:      test:

 85: TEST*/