usr/src/lib/libbc/libc/gen/common/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, Version 1.0 only
   6  * (the "License").  You may not use this file except in compliance
   7  * with the License.
   8  *
   9  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
  10  * or http://www.opensolaris.org/os/licensing.
  11  * See the License for the specific language governing permissions
  12  * and limitations under the License.
  13  *
  14  * When distributing Covered Code, include this CDDL HEADER in each
  15  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
  16  * If applicable, add the following below this CDDL HEADER, with the
  17  * fields enclosed by brackets "[]" replaced with your own identifying
  18  * information: Portions Copyright [yyyy] [name of copyright owner]
  19  *
  20  * CDDL HEADER END
  21  */
  22 /*
  23  * Copyright 1996 Sun Microsystems, Inc.  All rights reserved.
  24  * Use is subject to license terms.
  25  */
  26
  27 /*      Copyright (c) 1984 AT&T */
  28 /*        All Rights Reserved   */
  29
  30 #pragma ident   "%Z%%M% %I%     %E% SMI"
  31
  32 /*LINTLIBRARY*/
  33 /*
  34  *      drand48, etc. pseudo-random number generator
  35  *      This implementation assumes unsigned short integers of at least
  36  *      16 bits, long integers of at least 32 bits, and ignores
  37  *      overflows on adding or multiplying two unsigned integers.
  38  *      Two's-complement representation is assumed in a few places.
  39  *      Some extra masking is done if unsigneds are exactly 16 bits
  40  *      or longs are exactly 32 bits, but so what?
  41  *      An assembly-language implementation would run significantly faster.
  42  */
  43 #define N       16
  44 #define MASK    ((unsigned)(1 << (N - 1)) + (1 << (N - 1)) - 1)
  45 #define LOW(x)  ((unsigned)(x) & MASK)
  46 #define HIGH(x) LOW((x) >> N)
  47 #define MUL(x, y, z)    { long l = (long)(x) * (long)(y); \
  48                 (z)[0] = LOW(l); (z)[1] = HIGH(l); }
  49 #define CARRY(x, y)     ((long)(x) + (long)(y) > MASK)
  50 #define ADDEQU(x, y, z) (z = CARRY(x, (y)), x = LOW(x + (y)))
  51 #define X0      0x330E
  52 #define X1      0xABCD
  53 #define X2      0x1234
  54 #define A0      0xE66D
  55 #define A1      0xDEEC
  56 #define A2      0x5
  57 #define C       0xB
  58 #define SET3(x, x0, x1, x2)     ((x)[0] = (x0), (x)[1] = (x1), (x)[2] = (x2))
  59 #define SETLOW(x, y, n) SET3(x, LOW((y)[n]), LOW((y)[(n)+1]), LOW((y)[(n)+2]))
  60 #define SEED(x0, x1, x2) (SET3(x, x0, x1, x2), SET3(a, A0, A1, A2), c = C)
  61 #define REST(v)                                                 \
  62         for (i = 0; i < 3; i++) {                               \
  63                 xsubi[i] = x[i];                                \
  64                 x[i] = temp[i];                                 \
  65         }                                                       \
  66         return (v)
  67
  68 #define NEST(TYPE, f, F)                                        \
  69         TYPE f(xsubi)                                           \
  70         register unsigned short *xsubi;                         \
  71         {                                                       \
  72                 register int i;                                 \
  73                 register TYPE v;                                \
  74                 unsigned temp[3];                               \
  75                                                                 \
  76                 for (i = 0; i < 3; i++) {                       \
  77                         temp[i] = x[i];                         \
  78                         x[i] = LOW(xsubi[i]);                   \
  79                 }                                               \
  80                 v = F();                                        \
  81                 REST(v);                                        \
  82         }
  83
  84 static unsigned x[3] = { X0, X1, X2 }, a[3] = { A0, A1, A2 }, c = C;
  85 static unsigned short lastx[3];
  86 static void next();
  87
  88 double
  89 drand48()
  90 {
  91         static double two16m = 1.0 / (1L << N);
  92
  93         next();
  94         return (two16m * (two16m * (two16m * x[0] + x[1]) + x[2]));
  95 }
  96
  97 NEST(double, erand48, drand48)
  98
  99 long
 100 lrand48()
 101 {
 102         next();
 103         return (((long)x[2] << (N - 1)) + (x[1] >> 1));
 104 }
 105
 106 long
 107 mrand48()
 108 {
 109         next();
 110         return (((long)x[2] << N) + x[1]);
 111 }
 112
 113 static void
 114 next()
 115 {
 116         unsigned p[2], q[2], r[2], carry0, carry1;
 117
 118         MUL(a[0], x[0], p);
 119         ADDEQU(p[0], c, carry0);
 120         ADDEQU(p[1], carry0, carry1);
 121         MUL(a[0], x[1], q);
 122         ADDEQU(p[1], q[0], carry0);
 123         MUL(a[1], x[0], r);
 124         x[2] = LOW(carry0 + carry1 + CARRY(p[1], r[0]) + q[1] + r[1] +
 125                 a[0] * x[2] + a[1] * x[1] + a[2] * x[0]);
 126         x[1] = LOW(p[1] + r[0]);
 127         x[0] = LOW(p[0]);
 128 }
 129
 130 void
 131 srand48(seedval)
 132 long seedval;
 133 {
 134         SEED(X0, LOW(seedval), HIGH(seedval));
 135 }
 136
 137 unsigned short *
 138 seed48(seed16v)
 139 unsigned short seed16v[3];
 140 {
 141         SETLOW(lastx, x, 0);
 142         SEED(LOW(seed16v[0]), LOW(seed16v[1]), LOW(seed16v[2]));
 143         return (lastx);
 144 }
 145
 146 void
 147 lcong48(param)
 148 unsigned short param[7];
 149 {
 150         SETLOW(x, param, 0);
 151         SETLOW(a, param, 3);
 152         c = LOW(param[6]);
 153 }
 154
 155 NEST(long, nrand48, lrand48)
 156
 157 NEST(long, jrand48, mrand48)
 158
 159 #ifdef DRIVER
 160 /*
 161  *      This should print the sequences of integers in Tables 2
 162  *              and 1 of the TM:
 163  *      1623, 3442, 1447, 1829, 1305, ...
 164  *      657EB7255101, D72A0C966378, 5A743C062A23, ...
 165  */
 166 #include <stdio.h>
 167
 168 main()
 169 {
 170         int i;
 171
 172         for (i = 0; i < 80; i++) {
 173                 printf("%4d ", (int)(4096 * drand48()));
 174                 printf("%.4X%.4X%.4X\n", x[2], x[1], x[0]);
 175         }
 176 }
 177 #endif