random.c

/*-
 * Copyright (c) 1992, 1993
 *	The Regents of the University of California.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *	This product includes software developed by the University of
 *	California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 *	from: @(#)random.c	8.1 (Berkeley) 6/10/93
 *      $Id: random.c,v 1.5 2005/10/05 19:05:03 tomhart Exp $
 */

/*
 * Modified 4/10/2003 to allow parallel operation.
 * Copyright (c) 2003 IBM Corporation.
 */

#include "test.h"
#include "util.h"

/*
 * Initialize the random-number generator.
 */
void init_Random()
{
    /* Do nothing. */
}

/*
 * Set the seed for the current thread.
 */
void sRandom(unsigned long seed)
{
    this_thread.seed = seed;
}

/*
 * Pseudo-random number generator for randomizing the profiling clock,
 * and whatever else we might use it for.  The result is uniform on
 * [0, 2^31 - 1].
 */
unsigned long Random()
{
    register long x, hi, lo, t;

    /*
     * Compute x[n + 1] = (7^5 * x[n]) mod (2^31 - 1).
     * From "Random number generators: good ones are hard to find",
     * Park and Miller, Communications of the ACM, vol. 31, no. 10,
     * October 1988, p. 1195.
     */
    x = (long)this_thread.seed;
    hi = x / 127773;
    lo = x % 127773;
    t = 16807 * lo - 2836 * hi;
    if (t <= 0) {
        t += 0x7fffffff;
    }
    this_thread.seed = (unsigned long)t;
    return (unsigned long)t;
}