usr/src/lib/libc/port/gen/drand48.c

   1 /*
   2  * CDDL HEADER START
   3  *
   4  * The contents of this file are subject to the terms of the
   5  * Common Development and Distribution License (the "License").
   6  * You may not use this file except in compliance with the License.
   7  *
   8  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
   9  * or http://www.opensolaris.org/os/licensing.
  10  * See the License for the specific language governing permissions
  11  * and limitations under the License.
  12  *
  13  * When distributing Covered Code, include this CDDL HEADER in each
  14  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
  15  * If applicable, add the following below this CDDL HEADER, with the
  16  * fields enclosed by brackets "[]" replaced with your own identifying
  17  * information: Portions Copyright [yyyy] [name of copyright owner]
  18  *
  19  * CDDL HEADER END
  20  */
  21
  22 /*
  23  * Copyright 2008 Sun Microsystems, Inc.  All rights reserved.
  24  * Use is subject to license terms.
  25  */
  26
  27 /*      Copyright (c) 1988 AT&T */
  28 /*        All Rights Reserved   */
  29
  30 #pragma ident   "%Z%%M% %I%     %E% SMI"
  31
  32 /*
  33  *      drand48, etc. pseudo-random number generator
  34  *      This implementation assumes unsigned short integers of at least
  35  *      16 bits, long integers of at least 32 bits, and ignores
  36  *      overflows on adding or multiplying two unsigned integers.
  37  *      Two's-complement representation is assumed in a few places.
  38  *      Some extra masking is done if unsigneds are exactly 16 bits
  39  *      or longs are exactly 32 bits, but so what?
  40  *      An assembly-language implementation would run significantly faster.
  41  */
  42 /*
  43  *      New assumptions (supercede those stated above) for 64-bit work.
  44  *      Longs are now 64 bits, and we are bound by standards to return
  45  *      type long, hovever all internal calculations where long was
  46  *      previously used (32 bit precision) are now using the int32_t
  47  *      type (32 bit precision in both ILP32 and LP64 worlds).
  48  */
  49
  50 #include "lint.h"
  51 #include <mtlib.h>
  52 #include <synch.h>
  53 #include <thread.h>
  54
  55 static mutex_t seed_lock = DEFAULTMUTEX;
  56
  57 #define EXPORT0(TYPE, fn, fnu)  TYPE fn() { \
  58         TYPE res; \
  59         lmutex_lock(&seed_lock); \
  60         res = fnu(); \
  61         lmutex_unlock(&seed_lock); \
  62         return (res); }
  63 #define EXPORT1(TYPE, fn, fnu)  TYPE fn(unsigned short xsubi[3]) { \
  64         TYPE res; \
  65         lmutex_lock(&seed_lock); \
  66         res = fnu(xsubi); \
  67         lmutex_unlock(&seed_lock); \
  68         return (res); }
  69
  70 #define N       16
  71 #define MASK    ((unsigned)(1 << (N - 1)) + (1 << (N - 1)) - 1)
  72 #define LOW(x)  ((unsigned)(x) & MASK)
  73 #define HIGH(x) LOW((x) >> N)
  74 #define MUL(x, y, z)    { int32_t l = (int32_t)(x) * (int32_t)(y); \
  75                 (z)[0] = LOW(l); (z)[1] = HIGH(l); }
  76 #define CARRY(x, y)     ((int32_t)(x) + (int32_t)(y) > MASK)
  77 #define ADDEQU(x, y, z) (z = CARRY(x, (y)), x = LOW(x + (y)))
  78 #define X0      0x330E
  79 #define X1      0xABCD
  80 #define X2      0x1234
  81 #define A0      0xE66D
  82 #define A1      0xDEEC
  83 #define A2      0x5
  84 #define C       0xB
  85 #define SET3(x, x0, x1, x2)     ((x)[0] = (x0), (x)[1] = (x1), (x)[2] = (x2))
  86 #define SETLOW(x, y, n) SET3(x, LOW((y)[n]), LOW((y)[(n)+1]), LOW((y)[(n)+2]))
  87 #define SEED(x0, x1, x2) (SET3(x, x0, x1, x2), SET3(a, A0, A1, A2), c = C)
  88 #define REST(v) for (i = 0; i < 3; i++) { xsubi[i] = x[i]; x[i] = temp[i]; } \
  89                 return (v)
  90 #define NEST(TYPE, f, F) static TYPE f(unsigned short *xsubi) { \
  91         int i; TYPE v; unsigned temp[3]; \
  92         for (i = 0; i < 3; i++) { temp[i] = x[i]; x[i] = LOW(xsubi[i]); }  \
  93         v = F(); REST(v); }
  94
  95 /* Way ugly solution to problem names, but it works */
  96 #define x       _drand48_x
  97 #define a       _drand48_a
  98 #define c       _drand48_c
  99 /* End way ugly */
 100 static unsigned x[3] = { X0, X1, X2 }, a[3] = { A0, A1, A2 }, c = C;
 101 static unsigned short lastx[3];
 102 static void next(void);
 103
 104 static double
 105 _drand48_u(void)
 106 {
 107         static double two16m = 1.0 / ((int32_t)1 << N);
 108
 109         next();
 110         return (two16m * (two16m * (two16m * x[0] + x[1]) + x[2]));
 111 }
 112
 113 NEST(double, _erand48_u, _drand48_u)
 114
 115 static long
 116 _lrand48_u(void)
 117 {
 118         next();
 119         return ((long)((int32_t)x[2] << (N - 1)) + (x[1] >> 1));
 120 }
 121
 122 static long
 123 _mrand48_u(void)
 124 {
 125         next();
 126         return ((long)((int32_t)x[2] << N) + x[1]);
 127 }
 128
 129 static void
 130 next(void)
 131 {
 132         unsigned p[2], q[2], r[2], carry0, carry1;
 133
 134         MUL(a[0], x[0], p);
 135         ADDEQU(p[0], c, carry0);
 136         ADDEQU(p[1], carry0, carry1);
 137         MUL(a[0], x[1], q);
 138         ADDEQU(p[1], q[0], carry0);
 139         MUL(a[1], x[0], r);
 140         x[2] = LOW(carry0 + carry1 + CARRY(p[1], r[0]) + q[1] + r[1] +
 141             a[0] * x[2] + a[1] * x[1] + a[2] * x[0]);
 142         x[1] = LOW(p[1] + r[0]);
 143         x[0] = LOW(p[0]);
 144 }
 145
 146 void
 147 srand48(long seedval)
 148 {
 149         int32_t fixseed = (int32_t)seedval;     /* limit to 32 bits */
 150
 151         lmutex_lock(&seed_lock);
 152         SEED(X0, LOW(fixseed), HIGH(fixseed));
 153         lmutex_unlock(&seed_lock);
 154 }
 155
 156 unsigned short *
 157 seed48(unsigned short seed16v[3])
 158 {
 159         lmutex_lock(&seed_lock);
 160         SETLOW(lastx, x, 0);
 161         SEED(LOW(seed16v[0]), LOW(seed16v[1]), LOW(seed16v[2]));
 162         lmutex_unlock(&seed_lock);
 163         return (lastx);
 164 }
 165
 166 void
 167 lcong48(unsigned short param[7])
 168 {
 169         lmutex_lock(&seed_lock);
 170         SETLOW(x, param, 0);
 171         SETLOW(a, param, 3);
 172         c = LOW(param[6]);
 173         lmutex_unlock(&seed_lock);
 174 }
 175
 176 NEST(long, _nrand48_u, _lrand48_u)
 177
 178 NEST(long, _jrand48_u, _mrand48_u)
 179
 180 EXPORT0(double, drand48, _drand48_u)
 181 EXPORT1(double, erand48, _erand48_u)
 182
 183 EXPORT0(long, lrand48, _lrand48_u)
 184 EXPORT1(long, nrand48, _nrand48_u)
 185
 186 EXPORT0(long, mrand48, _mrand48_u)
 187 EXPORT1(long, jrand48, _jrand48_u)
 188
 189 #ifdef DRIVER
 190 /*
 191  *      This should print the sequences of integers in Tables 2
 192  *              and 1 of the TM:
 193  *      1623, 3442, 1447, 1829, 1305, ...
 194  *      657EB7255101, D72A0C966378, 5A743C062A23, ...
 195  */
 196 #include <stdio.h>
 197
 198 main()
 199 {
 200         int i;
 201
 202         for (i = 0; i < 80; i++) {
 203                 printf("%4d ", (int)(4096 * drand48()));
 204                 printf("%.4X%.4X%.4X\n", x[2], x[1], x[0]);
 205         }
 206 }
 207 #endif