random(3)                           CLIX                           random(3)



  NAME

    random, srandom - Provides a better random number generator

  LIBRARY

    Berkeley Software Distribution Library (libbsd.a)

  SYNOPSIS

    long random(
      void );

    void srandom(
      int seed );

  PARAMETERS

    seed   An integer used to seed the random number generator

  DESCRIPTION

    The random() function uses a nonlinear additive feedback random number
    generator.  The random() function employs a default table size of 31 long
    integers to return pseudo-random numbers in the range from 0 to 2^31-1.
    The period of this random number generator is approximately 16(2^31-1).

    The random() and srandom() functions have (almost) the same calling
    sequence and initialization properties as rand() and srand().  The
    difference is that rand() produces a much less random sequence.  In fact,
    the low dozen bits generated by rand() go through a cyclic pattern.  All
    the bits generated by random() are usable.  For example,

    random() & 01

    will produce a random binary value.  Unlike srand(), srandom() does not
    return the old seed because the amount of state information used is much
    more than a single word.  Like rand(), however, random() will by default
    produce a sequence of numbers that can be duplicated by calling srandom()
    with 1 as the seed.

    With 256 bytes of state information, the period of the random number
    generator is greater than 2^69, which should be sufficient for most
    purposes.

  EXAMPLES

    To create an array of 1000 random numbers using a seed of 16:

    #include <stdio.h>
    #include <math.h>



  2/94 - Intergraph Corporation                                              1

  random(3)                           CLIX                           random(3)



    main()
    {
         extern long random();
         extern void srandom();
         int random_array[1000];
         int i;
         srandom(16);
         for(i = 0; i <= 1000; i++) {
              random_array[i] = random();
              printf("%d\n", random_array[i]);
         }
    }


  NOTES

    The random() function executes at approximately  the speed of rand().

    To use the random() and srandom() functions, you must compile programs
    with the -lbsd flag to the cc command.

  RETURN VALUES

    The random() function and return pseudo-random numbers in the range from 0
    to 2^31-1.

  RELATED INFORMATION

    Functions:  rand(3)

























  2                                              Intergraph Corporation - 2/94