/*
  Pseudorandom Generator on 1996/12/ 5 by tutimura(a)nn.iij4u.or.jp
  http://www.nn.iij4u.or.jp/~tutimura/c/

  my_rand() returns a integer number between 0 and MY_RAND_MAX.
  MY_RAND_MAX == 65535 when using on gcc.
  my_srand(seed) sets random seed.

  They are similar to rand(), srand(), RAND_MAX in <stdlib.h>.
  The algorithm is based on linear congruential method,
  almost same as the one which ANSI explain as a sample.
  But this is not the best way.
  Use this to get same numbers independent from compilers.

  To get random numbers [0,N), calculate ( my_rand() % N ),
  or (int)( (double)my_rand() / (MY_RAND_MAX+1) * N ).
  Latter is slow but better.

  Not to get same numbers, do as below.
      #include <time.h>
      main() {
          my_srand( time(NULL) );
          ...
      }

  (updated on 2001/5/31)
  Please consult Mersenne Twister for a better random generator.
  (http://www.math.keio.ac.jp/~matumoto/mt.html)
*/

#include <limits.h>

#define MY_RAND_MAX             ( ULONG_MAX / 65536L )
#if UINT_MAX < MY_RAND_MAX
#undef  MY_RAND_MAX
#define MY_RAND_MAX             UINT_MAX
#endif

static unsigned long my_rand_seed = 1;

/* set seed */
void my_srand( unsigned long seed ) {
    my_rand_seed = seed;
}

/* generator */
unsigned my_rand( void ) {
    my_rand_seed *= 1103515245UL;
    my_rand_seed += 12345;
    return (unsigned)( my_rand_seed / 65536L );
}

#ifdef TEST
#include <stdio.h>
#include <stdlib.h>

void main() {
    int i;
    printf( "MY_RAND_MAX = %u\t", MY_RAND_MAX );
    printf( "   RAND_MAX = %u\n", RAND_MAX );

    for ( i=0; i<10; i++ ) {
        printf( "%6X - %6X\n", my_rand(), rand() );
    }
}
#endif