1: static char help[] = "Check the difference of the two matrices \n\
  2: Reads PETSc matrix A and B, then check B=A-B \n\
  3: Input parameters include\n\
  4:   -fA <input_file> -fB <input_file> \n\n";

  6:  #include <petscmat.h>

  8: #undef WRITEFILE
  9: PetscInt main(PetscInt argc,char **args)
 10: {
 11:   Mat            A,B;
 12:   PetscViewer    fd;
 13:   char           file[2][PETSC_MAX_PATH_LEN];
 14:   PetscBool      flg;
 16:   PetscMPIInt    size;
 17:   PetscInt       ma,na,mb,nb;

 19:   PetscInitialize(&argc,&args,(char*)0,help);if (ierr) return ierr;
 20:   MPI_Comm_size(PETSC_COMM_WORLD,&size);
 21:   if (size != 1) SETERRQ(PETSC_COMM_WORLD,PETSC_ERR_SUP,"This is a uniprocessor example only!");

 23:   /* read the two matrices, A and B */
 24:   PetscOptionsGetString(NULL,NULL,"-fA",file[0],PETSC_MAX_PATH_LEN,&flg);
 25:   if (!flg) SETERRQ(PETSC_COMM_WORLD,PETSC_ERR_USER,"Must indicate binary file with the -fA options");
 26:   PetscOptionsGetString(NULL,NULL,"-fB",file[1],PETSC_MAX_PATH_LEN,&flg);
 27:   if (!flg) SETERRQ(PETSC_COMM_WORLD,PETSC_ERR_USER,"Must indicate binary file with the -fP options");

 29:   /* Load matrices */
 30:   PetscViewerBinaryOpen(PETSC_COMM_WORLD,file[0],FILE_MODE_READ,&fd);
 31:   MatCreate(PETSC_COMM_WORLD,&A);
 32:   MatLoad(A,fd);
 33:   PetscViewerDestroy(&fd);
 34:   printf("\n A:\n");
 35:   printf("----------------------\n");
 36:   MatView(A,PETSC_VIEWER_STDOUT_WORLD);
 37:   MatGetSize(A,&ma,&na);

 39:   PetscViewerBinaryOpen(PETSC_COMM_WORLD,file[1],FILE_MODE_READ,&fd);
 40:   MatCreate(PETSC_COMM_WORLD,&B);
 41:   MatLoad(B,fd);
 42:   PetscViewerDestroy(&fd);
 43:   printf("\n B:\n");
 44:   printf("----------------------\n");
 45:   MatView(B,PETSC_VIEWER_STDOUT_WORLD);
 46:   MatGetSize(B,&mb,&nb);

 48:   /* Compute B = -A + B */
 49:   if (ma != mb || na != nb) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_ARG_SIZ,"nonconforming matrix size");
 50:   MatAXPY(B,-1.0,A,DIFFERENT_NONZERO_PATTERN);
 51:   printf("\n B - A:\n");
 52:   printf("----------------------\n");
 53:   MatView(B,PETSC_VIEWER_STDOUT_WORLD);

 55:   MatDestroy(&B);
 56:   MatDestroy(&A);
 57:   PetscFinalize();
 58:   return ierr;
 59: }