src/util/random.c File Reference
#include "util.h"
Go to the source code of this file.
Defines | |
| #define | MODULUS1 2147483563 |
| #define | LEQA1 40014 |
| #define | LEQQ1 53668 |
| #define | LEQR1 12211 |
| #define | MODULUS2 2147483399 |
| #define | LEQA2 40692 |
| #define | LEQQ2 52774 |
| #define | LEQR2 3791 |
| #define | STAB_SIZE 64 |
| #define | STAB_DIV (1 + (MODULUS1 - 1) / STAB_SIZE) |
Functions | |
| void | util_srandom (long seed) |
| long | util_random (void) |
Variables | |
| static char rcsid[] | UNUSED = "$Id: random.c,v 1.4 2002/09/10 00:05:33 fabio Exp $" |
| static long | utilRand = 0 |
| static long | utilRand2 |
| static long | shuffleSelect |
| static long | shuffleTable [STAB_SIZE] |
Define Documentation
Function Documentation
| long util_random | ( | void | ) |
Function********************************************************************
Synopsis [Portable random number generator.]
Description [Portable number generator based on ran2 from "Numerical Recipes in C." It is a long period (> 2 * 10^18) random number generator of L'Ecuyer with Bays-Durham shuffle. Returns a long integer uniformly distributed between 0 and 2147483561 (inclusive of the endpoint values). The random generator can be explicitly initialized by calling util_srandom. If no explicit initialization is performed, then the seed 1 is assumed.]
SideEffects []
SeeAlso [util_srandom]
Definition at line 143 of file random.c.
00144 { 00145 int i; /* index in the shuffle table */ 00146 long int w; /* work variable */ 00147 00148 /* utilRand == 0 if the geneartor has not been initialized yet. */ 00149 if (utilRand == 0) util_srandom(1); 00150 00151 /* Compute utilRand = (utilRand * LEQA1) % MODULUS1 avoiding 00152 ** overflows by Schrage's method. 00153 */ 00154 w = utilRand / LEQQ1; 00155 utilRand = LEQA1 * (utilRand - w * LEQQ1) - w * LEQR1; 00156 utilRand += (utilRand < 0) * MODULUS1; 00157 00158 /* Compute utilRand2 = (utilRand2 * LEQA2) % MODULUS2 avoiding 00159 ** overflows by Schrage's method. 00160 */ 00161 w = utilRand2 / LEQQ2; 00162 utilRand2 = LEQA2 * (utilRand2 - w * LEQQ2) - w * LEQR2; 00163 utilRand2 += (utilRand2 < 0) * MODULUS2; 00164 00165 /* utilRand is shuffled with the Bays-Durham algorithm. 00166 ** shuffleSelect and utilRand2 are combined to generate the output. 00167 */ 00168 00169 /* Pick one element from the shuffle table; "i" will be in the range 00170 ** from 0 to STAB_SIZE-1. 00171 */ 00172 i = shuffleSelect / STAB_DIV; 00173 /* Mix the element of the shuffle table with the current iterate of 00174 ** the second sub-generator, and replace the chosen element of the 00175 ** shuffle table with the current iterate of the first sub-generator. 00176 */ 00177 shuffleSelect = shuffleTable[i] - utilRand2; 00178 shuffleTable[i] = utilRand; 00179 shuffleSelect += (shuffleSelect < 1) * (MODULUS1 - 1); 00180 /* Since shuffleSelect != 0, and we want to be able to return 0, 00181 ** here we subtract 1 before returning. 00182 */ 00183 return(shuffleSelect - 1); 00184 00185 } /* end of util_random */
| void util_srandom | ( | long | seed | ) |
AutomaticStart AutomaticEnd Function********************************************************************
Synopsis [Initializer for the portable random number generator.]
Description [Initializer for the portable number generator based on ran2 in "Numerical Recipes in C." The input is the seed for the generator. If it is negative, its absolute value is taken as seed. If it is 0, then 1 is taken as seed. The initialized sets up the two recurrences used to generate a long-period stream, and sets up the shuffle table.]
SideEffects [None]
SeeAlso [util_random]
Definition at line 106 of file random.c.
00107 { 00108 int i; 00109 00110 if (seed < 0) utilRand = -seed; 00111 else if (seed == 0) utilRand = 1; 00112 else utilRand = seed; 00113 utilRand2 = utilRand; 00114 /* Load the shuffle table (after 11 warm-ups). */ 00115 for (i = 0; i < STAB_SIZE + 11; i++) { 00116 long int w; 00117 w = utilRand / LEQQ1; 00118 utilRand = LEQA1 * (utilRand - w * LEQQ1) - w * LEQR1; 00119 utilRand += (utilRand < 0) * MODULUS1; 00120 shuffleTable[i % STAB_SIZE] = utilRand; 00121 } 00122 shuffleSelect = shuffleTable[1 % STAB_SIZE]; 00123 } /* end of util_srandom */
Variable Documentation
long shuffleSelect [static] |
long shuffleTable[STAB_SIZE] [static] |
char rcsid [] UNUSED = "$Id: random.c,v 1.4 2002/09/10 00:05:33 fabio Exp $" [static] |
CFile***********************************************************************
FileName [random.c]
PackageName [util]
Synopsis [Our own portable random number generator.]
Author [Fabio Somenzi <Fabio@Colorado.EDU>]
Copyright [Copyright (c) 1994-1996 The Regents of the Univ. of California. All rights reserved.
Permission is hereby granted, without written agreement and without license or royalty fees, to use, copy, modify, and distribute this software and its documentation for any purpose, provided that the above copyright notice and the following two paragraphs appear in all copies of this software.
IN NO EVENT SHALL THE UNIVERSITY OF CALIFORNIA BE LIABLE TO ANY PARTY FOR DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS DOCUMENTATION, EVEN IF THE UNIVERSITY OF CALIFORNIA HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
THE UNIVERSITY OF CALIFORNIA SPECIFICALLY DISCLAIMS ANY WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE SOFTWARE PROVIDED HEREUNDER IS ON AN \"AS IS\" BASIS, AND THE UNIVERSITY OF CALIFORNIA HAS NO OBLIGATION TO PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.]
