2: static char help[] = "Reads a PETSc matrix and vector from a file and reorders it.\n\
  3:   -f0 <input_file> : first file to load (small system)\n\
  4:   -f1 <input_file> : second file to load (larger system)\n\n";

  6: /*T
  7:    Concepts: Mat^ordering a matrix - loading a binary matrix and vector;
  8:    Concepts: Mat^loading a binary matrix and vector;
  9:    Concepts: Vectors^loading a binary vector;
 10:    Concepts: PetscLog^preloading executable
 11:    Processors: 1
 12: T*/

 14: /*
 15:   Include "petscmat.h" so that we can use matrices.
 16:   automatically includes:
 17:      petscsys.h       - base PETSc routines   petscvec.h    - vectors
 18:      petscmat.h    - matrices
 19:      petscis.h     - index sets            petscviewer.h - viewers
 20: */
 21: #include <petscmat.h>

 25: int main(int argc,char **args)
 26: {
 27:   Mat             A;                      /* matrix */
 28:   PetscViewer     fd;                     /* viewer */
 29:   char            file[2][PETSC_MAX_PATH_LEN];           /* input file name */
 30:   IS              isrow,iscol;            /* row and column permutations */
 31:   PetscErrorCode  ierr;
 32:   MatOrderingType rtype = MATORDERINGRCM;
 33:   PetscBool       flg,PetscPreLoad = PETSC_FALSE;

 35:   PetscInitialize(&argc,&args,(char*)0,help);


 38:   /*
 39:      Determine files from which we read the two linear systems
 40:      (matrix and right-hand-side vector).
 41:   */
 42:   PetscOptionsGetString(NULL,NULL,"-f0",file[0],PETSC_MAX_PATH_LEN,&flg);
 43:   if (!flg) SETERRQ(PETSC_COMM_WORLD,1,"Must indicate binary file with the -f0 option");
 44:   PetscOptionsGetString(NULL,NULL,"-f1",file[1],PETSC_MAX_PATH_LEN,&flg);
 45:   if (flg) PetscPreLoad = PETSC_TRUE;

 47:   /* -----------------------------------------------------------
 48:                   Beginning of loop
 49:      ----------------------------------------------------------- */
 50:   /*
 51:      Loop through the reordering 2 times.
 52:       - The intention here is to preload and solve a small system;
 53:         then load another (larger) system and solve it as well.
 54:         This process preloads the instructions with the smaller
 55:         system so that more accurate performance monitoring (via
 56:         -log_summary) can be done with the larger one (that actually
 57:         is the system of interest).
 58:   */
 59:   PetscPreLoadBegin(PetscPreLoad,"Load");

 61:   /* - - - - - - - - - - - New Stage - - - - - - - - - - - - -
 62:                          Load system i
 63:    - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

 65:   /*
 66:      Open binary file.  Note that we use FILE_MODE_READ to indicate
 67:      reading from this file.
 68:   */
 69:   PetscViewerBinaryOpen(PETSC_COMM_WORLD,file[PetscPreLoadIt],FILE_MODE_READ,&fd);

 71:   /*
 72:      Load the matrix; then destroy the viewer.
 73:   */
 74:   MatCreate(PETSC_COMM_WORLD,&A);
 75:   MatSetType(A,MATSEQAIJ);
 76:   MatLoad(A,fd);
 77:   PetscViewerDestroy(&fd);


 80:   /* - - - - - - - - - - - New Stage - - - - - - - - - - - - -
 81:    - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

 83:   PetscPreLoadStage("Reordering");
 84:   MatGetOrdering(A,rtype,&isrow,&iscol);

 86:   /*
 87:      Free work space.  All PETSc objects should be destroyed when they
 88:      are no longer needed.
 89:   */
 90:   MatDestroy(&A);
 91:   ISDestroy(&isrow);
 92:   ISDestroy(&iscol);
 93:   PetscPreLoadEnd();

 95:   PetscFinalize();
 96:   return 0;
 97: }