gen/common/drand48.c

/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License, Version 1.0 only
 * (the "License").  You may not use this file except in compliance
 * with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */
/*
 * Copyright 1996 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

/*      Copyright (c) 1984 AT&T */
/*        All Rights Reserved   */

#pragma ident   "%Z%%M% %I% %E% SMI"

/*LINTLIBRARY*/
/*
 *  drand48, etc. pseudo-random number generator
 *  This implementation assumes unsigned short integers of at least
 *  16 bits, long integers of at least 32 bits, and ignores
 *  overflows on adding or multiplying two unsigned integers.
 *  Two's-complement representation is assumed in a few places.
 *  Some extra masking is done if unsigneds are exactly 16 bits
 *  or longs are exactly 32 bits, but so what?
 *  An assembly-language implementation would run significantly faster.
 */
#define N   16
#define MASK    ((unsigned)(1 << (N - 1)) + (1 << (N - 1)) - 1)
#define LOW(x)  ((unsigned)(x) & MASK)
#define HIGH(x) LOW((x) >> N)
#define MUL(x, y, z)    { long l = (long)(x) * (long)(y); \
        (z)[0] = LOW(l); (z)[1] = HIGH(l); }
#define CARRY(x, y) ((long)(x) + (long)(y) > MASK)
#define ADDEQU(x, y, z) (z = CARRY(x, (y)), x = LOW(x + (y)))
#define X0  0x330E
#define X1  0xABCD
#define X2  0x1234
#define A0  0xE66D
#define A1  0xDEEC
#define A2  0x5
#define C   0xB
#define SET3(x, x0, x1, x2) ((x)[0] = (x0), (x)[1] = (x1), (x)[2] = (x2))
#define SETLOW(x, y, n) SET3(x, LOW((y)[n]), LOW((y)[(n)+1]), LOW((y)[(n)+2]))
#define SEED(x0, x1, x2) (SET3(x, x0, x1, x2), SET3(a, A0, A1, A2), c = C)
#define REST(v)                         \
    for (i = 0; i < 3; i++) {               \
        xsubi[i] = x[i];                \
        x[i] = temp[i];                 \
    }                           \
    return (v)

#define NEST(TYPE, f, F)                    \
    TYPE f(xsubi)                       \
    register unsigned short *xsubi;             \
    {                           \
        register int i;                 \
        register TYPE v;                \
        unsigned temp[3];               \
                                \
        for (i = 0; i < 3; i++) {           \
            temp[i] = x[i];             \
            x[i] = LOW(xsubi[i]);           \
        }                       \
        v = F();                    \
        REST(v);                    \
    }

static unsigned x[3] = { X0, X1, X2 }, a[3] = { A0, A1, A2 }, c = C;
static unsigned short lastx[3];
static void next();

double
drand48()
{
    static double two16m = 1.0 / (1L << N);

    next();
    return (two16m * (two16m * (two16m * x[0] + x[1]) + x[2]));
}

NEST(double, erand48, drand48)

long
lrand48()
{
    next();
    return (((long)x[2] << (N - 1)) + (x[1] >> 1));
}

long
mrand48()
{
    next();
    return (((long)x[2] << N) + x[1]);
}

static void
next()
{
    unsigned p[2], q[2], r[2], carry0, carry1;

    MUL(a[0], x[0], p);
    ADDEQU(p[0], c, carry0);
    ADDEQU(p[1], carry0, carry1);
    MUL(a[0], x[1], q);
    ADDEQU(p[1], q[0], carry0);
    MUL(a[1], x[0], r);
    x[2] = LOW(carry0 + carry1 + CARRY(p[1], r[0]) + q[1] + r[1] +
        a[0] * x[2] + a[1] * x[1] + a[2] * x[0]);
    x[1] = LOW(p[1] + r[0]);
    x[0] = LOW(p[0]);
}

void
srand48(seedval)
long seedval;
{
    SEED(X0, LOW(seedval), HIGH(seedval));
}

unsigned short *
seed48(seed16v)
unsigned short seed16v[3];
{
    SETLOW(lastx, x, 0);
    SEED(LOW(seed16v[0]), LOW(seed16v[1]), LOW(seed16v[2]));
    return (lastx);
}

void
lcong48(param)
unsigned short param[7];
{
    SETLOW(x, param, 0);
    SETLOW(a, param, 3);
    c = LOW(param[6]);
}

NEST(long, nrand48, lrand48)

NEST(long, jrand48, mrand48)

#ifdef DRIVER
/*
 *  This should print the sequences of integers in Tables 2
 *      and 1 of the TM:
 *  1623, 3442, 1447, 1829, 1305, ...
 *  657EB7255101, D72A0C966378, 5A743C062A23, ...
 */
#include <stdio.h>

main()
{
    int i;

    for (i = 0; i < 80; i++) {
        printf("%4d ", (int)(4096 * drand48()));
        printf("%.4X%.4X%.4X\n", x[2], x[1], x[0]);
    }
}
#endif