Actual source code: ex1.c
petsc-3.12.4 2020-02-04
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      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>

     23: int main(int argc,char **args)
     24: {
     25:   Mat             A;                      /* matrix */
     26:   PetscViewer     fd;                     /* viewer */
     27:   char            file[PETSC_MAX_PATH_LEN];           /* input file name */
     28:   IS              isrow,iscol;            /* row and column permutations */
     29:   PetscErrorCode  ierr;
     30:   MatOrderingType rtype = MATORDERINGRCM;
     31:   PetscBool       flg;

     33:   PetscInitialize(&argc,&args,(char*)0,help);if (ierr) return ierr;
     34:   /*
     35:      Determine files from which we read the two linear systems
     36:      (matrix and right-hand-side vector).
     37:   */
     38:   PetscOptionsGetString(NULL,NULL,"-f",file,PETSC_MAX_PATH_LEN,&flg);
     39:   if (!flg) SETERRQ(PETSC_COMM_WORLD,1,"Must indicate binary file with the -f option");

     41:   /* -----------------------------------------------------------
     42:                   Beginning of loop
     43:      ----------------------------------------------------------- */
     44:   /*
     45:      Loop through the reordering 2 times.
     46:       - The intention here is to preload and solve a small system;
     47:         then load another (larger) system and solve it as well.
     48:         This process preloads the instructions with the smaller
     49:         system so that more accurate performance monitoring (via
     50:         -log_view) can be done with the larger one (that actually
     51:         is the system of interest).
     52:   */

     54:   /* - - - - - - - - - - - New Stage - - - - - - - - - - - - -
     55:                          Load system i
     56:    - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

     58:   /*
     59:      Open binary file.  Note that we use FILE_MODE_READ to indicate
     60:      reading from this file.
     61:   */
     62:   PetscViewerBinaryOpen(PETSC_COMM_WORLD,file,FILE_MODE_READ,&fd);

     64:   /*
     65:      Load the matrix; then destroy the viewer.
     66:   */
     67:   MatCreate(PETSC_COMM_WORLD,&A);
     68:   MatSetType(A,MATSEQAIJ);
     69:   MatLoad(A,fd);
     70:   PetscViewerDestroy(&fd);

     72:   MatGetOrdering(A,rtype,&isrow,&iscol);
     73:   ISView(isrow,PETSC_VIEWER_STDOUT_WORLD);

     75:   /*
     76:      Free work space.  All PETSc objects should be destroyed when they
     77:      are no longer needed.
     78:   */
     79:   MatDestroy(&A);
     80:   ISDestroy(&isrow);
     81:   ISDestroy(&iscol);

     83:   PetscFinalize();
     84:   return ierr;
     85: }

     89: /*TEST

     91:    test:
     92:       requires: datafilespath double !complex !define(PETSC_USE_64BIT_INDICES)
     93:       args: -f ${DATAFILESPATH}/matrices/medium -viewer_binary_skip_info

     95: TEST*/