text: /* -*- Mode: C; c-basic-offset:4 ; indent-tabs-mode:nil ; -*- */
  /*
   *  (C) 2001 by Argonne National Laboratory.
   *      See COPYRIGHT in top-level directory.
   */
  #include "mpi.h"
  #include <stdio.h>
  #include <string.h>
  #include <stdlib.h>
  
  /* tests noncontiguous reads/writes using independent I/O */
  
  #define SIZE 5000
  
  #define VERBOSE 0
  int main(int argc, char **argv)
  {
      int *buf, i, mynod, nprocs, len, b[3];
      int errs = 0, toterrs;
      MPI_Aint d[3];
      MPI_File fh;
      MPI_Status status;
      char *filename;
      MPI_Datatype typevec, newtype, t[3];
      MPI_Info info;
  
      MPI_Init(&argc, &argv);
      MPI_Comm_size(MPI_COMM_WORLD, &nprocs);
      MPI_Comm_rank(MPI_COMM_WORLD, &mynod);
  
      if (nprocs != 2) {
          fprintf(stderr, "Run this program on two processes\n");
          MPI_Abort(MPI_COMM_WORLD, 1);
      }
  
  /* process 0 takes the file name as a command-line argument and
     broadcasts it to other processes (length first, then string) */
      if (!mynod) {
          i = 1;
          while ((i < argc) && strcmp("-fname", *argv)) {
              i++;
              argv++;
          }
          if (i >= argc) {
              fprintf(stderr, "\n*#  Usage: noncontig -fname filename\n\n");
              MPI_Abort(MPI_COMM_WORLD, 1);
          }
          argv++;
          len = strlen(*argv);
          filename = (char *) malloc(len + 1);
          strcpy(filename, *argv);
          MPI_Bcast(&len, 1, MPI_INT, 0, MPI_COMM_WORLD);
          MPI_Bcast(filename, len + 1, MPI_CHAR, 0, MPI_COMM_WORLD);
      } else {
          MPI_Bcast(&len, 1, MPI_INT, 0, MPI_COMM_WORLD);
          filename = (char *) malloc(len + 1);
          MPI_Bcast(filename, len + 1, MPI_CHAR, 0, MPI_COMM_WORLD);
      }
  
      buf = (int *) malloc(SIZE * sizeof(int));
  
      MPI_Type_vector(SIZE / 2, 1, 2, MPI_INT, &typevec);
  
      /* create a struct type with explicitly set LB and UB; displacements
       * of typevec are such that the types for the two processes won't
       * overlap.
       */
      b[0] = b[1] = b[2] = 1;
      d[0] = 0;
      d[1] = mynod * sizeof(int);
      d[2] = SIZE * sizeof(int);
      t[0] = MPI_LB;
      t[1] = typevec;
      t[2] = MPI_UB;
  
      /* keep the struct, ditch the vector */
      MPI_Type_struct(3, b, d, t, &newtype);
      MPI_Type_commit(&newtype);
      MPI_Type_free(&typevec);
  
      MPI_Info_create(&info);
      /* I am setting these info values for testing purposes only. It is
       * better to use the default values in practice. */
      MPI_Info_set(info, "ind_rd_buffer_size", "1209");
      MPI_Info_set(info, "ind_wr_buffer_size", "1107");
  
      if (!mynod) {
  #if VERBOSE
          fprintf(stderr,
                  "\ntesting noncontiguous in memory, noncontiguous in file using independent I/O\n");
  #endif
          MPI_File_delete(filename, MPI_INFO_NULL);
      }
      MPI_Barrier(MPI_COMM_WORLD);
  
      MPI_File_open(MPI_COMM_WORLD, filename, MPI_MODE_CREATE | MPI_MODE_RDWR, info, &fh);
  
      /* set the file view for each process -- now writes go into the non-
       * overlapping but interleaved region defined by the struct type up above
       */
      MPI_File_set_view(fh, 0, MPI_INT, newtype, "native", info);
  
      /* fill our buffer with a pattern and write, using our type again */
      for (i = 0; i < SIZE; i++)
          buf[i] = i + mynod * SIZE;
      MPI_File_write(fh, buf, 1, newtype, &status);
  
      MPI_Barrier(MPI_COMM_WORLD);
  
      /* fill the entire buffer with -1's.  read back with type.
       * note that the result of this read should be that every other value
       * in the buffer is still -1, as defined by our type.
       */
      for (i = 0; i < SIZE; i++)
          buf[i] = -1;
      MPI_File_read_at(fh, 0, buf, 1, newtype, &status);
  
      /* check that all the values read are correct and also that we didn't
       * overwrite any of the -1 values that we shouldn't have.
       */
      for (i = 0; i < SIZE; i++) {
          if (!mynod) {
              if ((i % 2) && (buf[i] != -1)) {
                  errs++;
                  fprintf(stderr, "Process %d: buf %d is %d, should be -1\n", mynod, i, buf[i]);
              }
              if (!(i % 2) && (buf[i] != i)) {
                  errs++;
                  fprintf(stderr, "Process %d: buf %d is %d, should be %d\n", mynod, i, buf[i], i);
              }
          } else {
              if ((i % 2) && (buf[i] != i + mynod * SIZE)) {
                  errs++;
                  fprintf(stderr, "Process %d: buf %d is %d, should be %d\n",
                          mynod, i, buf[i], i + mynod * SIZE);
              }
              if (!(i % 2) && (buf[i] != -1)) {
                  errs++;
                  fprintf(stderr, "Process %d: buf %d is %d, should be -1\n", mynod, i, buf[i]);
              }
          }
      }
  
      MPI_File_close(&fh);
  
      MPI_Barrier(MPI_COMM_WORLD);
  
      if (!mynod) {
  #if VERBOSE
          fprintf(stderr,
                  "\ntesting noncontiguous in memory, contiguous in file using independent I/O\n");
  #endif
          MPI_File_delete(filename, MPI_INFO_NULL);
      }
      MPI_Barrier(MPI_COMM_WORLD);
  
      MPI_File_open(MPI_COMM_WORLD, filename, MPI_MODE_CREATE | MPI_MODE_RDWR, info, &fh);
  
      /* in this case we write to either the first half or the second half
       * of the file space, so the regions are not interleaved.  this is done
       * by leaving the file view at its default.
       */
      for (i = 0; i < SIZE; i++)
          buf[i] = i + mynod * SIZE;
      MPI_File_write_at(fh, mynod * (SIZE / 2) * sizeof(int), buf, 1, newtype, &status);
  
      MPI_Barrier(MPI_COMM_WORLD);
  
      /* same as before; fill buffer with -1's and then read; every other
       * value should still be -1 after the read
       */
      for (i = 0; i < SIZE; i++)
          buf[i] = -1;
      MPI_File_read_at(fh, mynod * (SIZE / 2) * sizeof(int), buf, 1, newtype, &status);
  
      /* verify that the buffer looks like it should */
      for (i = 0; i < SIZE; i++) {
          if (!mynod) {
              if ((i % 2) && (buf[i] != -1)) {
                  errs++;
                  fprintf(stderr, "Process %d: buf %d is %d, should be -1\n", mynod, i, buf[i]);
              }
              if (!(i % 2) && (buf[i] != i)) {
                  errs++;
                  fprintf(stderr, "Process %d: buf %d is %d, should be %d\n", mynod, i, buf[i], i);
              }
          } else {
              if ((i % 2) && (buf[i] != i + mynod * SIZE)) {
                  errs++;
                  fprintf(stderr, "Process %d: buf %d is %d, should be %d\n",
                          mynod, i, buf[i], i + mynod * SIZE);
              }
              if (!(i % 2) && (buf[i] != -1)) {
                  errs++;
                  fprintf(stderr, "Process %d: buf %d is %d, should be -1\n", mynod, i, buf[i]);
              }
          }
      }
  
      MPI_File_close(&fh);
  
      MPI_Barrier(MPI_COMM_WORLD);
  
      if (!mynod) {
  #if VERBOSE
          fprintf(stderr,
                  "\ntesting contiguous in memory, noncontiguous in file using independent I/O\n");
  #endif
          MPI_File_delete(filename, MPI_INFO_NULL);
      }
      MPI_Barrier(MPI_COMM_WORLD);
  
      MPI_File_open(MPI_COMM_WORLD, filename, MPI_MODE_CREATE | MPI_MODE_RDWR, info, &fh);
  
      /* set the file view so that we have interleaved access again */
      MPI_File_set_view(fh, 0, MPI_INT, newtype, "native", info);
  
      /* this time write a contiguous buffer */
      for (i = 0; i < SIZE; i++)
          buf[i] = i + mynod * SIZE;
      MPI_File_write(fh, buf, SIZE, MPI_INT, &status);
  
      MPI_Barrier(MPI_COMM_WORLD);
  
      /* fill buffer with -1's; this time they will all be overwritten */
      for (i = 0; i < SIZE; i++)
          buf[i] = -1;
      MPI_File_read_at(fh, 0, buf, SIZE, MPI_INT, &status);
  
      for (i = 0; i < SIZE; i++) {
          if (!mynod) {
              if (buf[i] != i) {
                  errs++;
                  fprintf(stderr, "Process %d: buf %d is %d, should be %d\n", mynod, i, buf[i], i);
              }
          } else {
              if (buf[i] != i + mynod * SIZE) {
                  errs++;
                  fprintf(stderr, "Process %d: buf %d is %d, should be %d\n",
                          mynod, i, buf[i], i + mynod * SIZE);
              }
          }
      }
  
      MPI_File_close(&fh);
  
      MPI_Allreduce(&errs, &toterrs, 1, MPI_INT, MPI_SUM, MPI_COMM_WORLD);
      if (mynod == 0) {
          if (toterrs > 0) {
              fprintf(stderr, "Found %d errors\n", toterrs);
          } else {
              fprintf(stdout, " No Errors\n");
          }
      }
      MPI_Type_free(&newtype);
      MPI_Info_free(&info);
      free(buf);
      free(filename);
      MPI_Finalize();
      return 0;
  }
  