parallel-merge.c

/* Generates about 1 MB of random data that is then divided into
   16 chunks.  A separate subprocess sorts each chunk; the
   subprocesses run in parallel.  Then we merge the chunks and
   verify that the result is what it should be. */

#include "tests/vm/parallel-merge.h"
#include <stdio.h>
#include <syscall.h>
#include "tests/arc4.h"
#include "tests/lib.h"
#include "tests/main.h"

#define CHUNK_SIZE (128 * 1024)
#define CHUNK_CNT 8                             /* Number of chunks. */
#define DATA_SIZE (CHUNK_CNT * CHUNK_SIZE)      /* Buffer size. */

unsigned char buf1[DATA_SIZE], buf2[DATA_SIZE];
size_t histogram[256];

/* Initialize buf1 with random data,
   then count the number of instances of each value within it. */
static void
init (void) 
{
  struct arc4 arc4;
  size_t i;

  msg ("init");

  arc4_init (&arc4, "foobar", 6);
  arc4_crypt (&arc4, buf1, sizeof buf1);
  for (i = 0; i < sizeof buf1; i++)
    histogram[buf1[i]]++;
}

/* Sort each chunk of buf1 using SUBPROCESS,
   which is expected to return EXIT_STATUS. */
static void
sort_chunks (const char *subprocess, int exit_status)
{
  pid_t children[CHUNK_CNT];
  size_t i;

  for (i = 0; i < CHUNK_CNT; i++) 
    {
      char fn[128];
      char cmd[128];
      int handle;

      msg ("sort chunk %zu", i);

      /* Write this chunk to a file. */
      snprintf (fn, sizeof fn, "buf%zu", i);
      create (fn, CHUNK_SIZE);
      quiet = true;
      CHECK ((handle = open (fn)) > 1, "open \"%s\"", fn);
      write (handle, buf1 + CHUNK_SIZE * i, CHUNK_SIZE);
      close (handle);

      /* Sort with subprocess. */
      snprintf (cmd, sizeof cmd, "%s %s", subprocess, fn);
      CHECK ((children[i] = exec (cmd)) != -1, "exec \"%s\"", cmd);
      quiet = false;
    }

  for (i = 0; i < CHUNK_CNT; i++) 
    {
      char fn[128];
      int handle;