1 /* Copyright (c) 2007, 2008, 2009, 2010. The SimGrid Team.
2 * All rights reserved. */
4 /* This program is free software; you can redistribute it and/or modify it
5 * under the terms of the license (GNU LGPL) which comes with this package. */
7 #include "surf/random_mgr.h"
8 #include "xbt/sysdep.h"
9 #include "gras_config.h" /*_XBT_WIN32*/
11 XBT_LOG_NEW_DEFAULT_SUBCATEGORY(random, surf, "Random part of surf");
15 static unsigned int _seed = 2147483647;
18 typedef unsigned __int64 uint64_t;
19 typedef unsigned int uint32_t;
23 unsigned short int __x[3]; /* Current state. */
24 unsigned short int __old_x[3]; /* Old state. */
25 unsigned short int __c; /* Additive const. in congruential formula. */
26 unsigned short int __init; /* Flag for initializing. */
27 unsigned long long int __a; /* Factor in congruential formula. */
30 static struct drand48_data __libc_drand48_data = { 0 };
32 union ieee754_double {
35 /* This is the IEEE 754 double-precision format. */
37 /* Together these comprise the mantissa. */
38 unsigned int mantissa1:32;
39 unsigned int mantissa0:20;
40 unsigned int exponent:11;
41 unsigned int negative:1;
45 /* This format makes it easier to see if a NaN is a signalling NaN. */
47 /* Together these comprise the mantissa. */
48 unsigned int mantissa1:32;
49 unsigned int mantissa0:19;
50 unsigned int quiet_nan:1;
51 unsigned int exponent:11;
52 unsigned int negative:1;
57 #define IEEE754_DOUBLE_BIAS 0x3ff /* Added to exponent. */
62 _drand48_iterate(unsigned short int xsubi[3], struct drand48_data *buffer);
65 _erand48_r(unsigned short int xsubi[3], struct drand48_data *buffer,
70 _erand48_r(unsigned short int xsubi[3], struct drand48_data *buffer,
73 union ieee754_double temp;
75 /* Compute next state. */
76 if (_drand48_iterate(xsubi, buffer) < 0)
79 /* Construct a positive double with the 48 random bits distributed over
80 its fractional part so the resulting FP number is [0.0,1.0). */
82 temp.ieee.negative = 0;
83 temp.ieee.exponent = IEEE754_DOUBLE_BIAS;
84 temp.ieee.mantissa0 = (xsubi[2] << 4) | (xsubi[1] >> 12);
85 temp.ieee.mantissa1 = ((xsubi[1] & 0xfff) << 20) | (xsubi[0] << 4);
87 /* Please note the lower 4 bits of mantissa1 are always 0. */
88 *result = temp.d - 1.0;
93 int _drand48_iterate(unsigned short int xsubi[3],
94 struct drand48_data *buffer)
99 /* Initialize buffer, if not yet done. */
101 if (buffer->__init == 0) {
102 buffer->__a = 0x5deece66dull;
107 /* Do the real work. We choose a data type which contains at least
108 48 bits. Because we compute the modulus it does not care how
109 many bits really are computed. */
111 X = (uint64_t) xsubi[2] << 32 | (uint32_t) xsubi[1] << 16 | xsubi[0];
113 result = X * buffer->__a + buffer->__c;
116 xsubi[0] = result & 0xffff;
117 xsubi[1] = (result >> 16) & 0xffff;
118 xsubi[2] = (result >> 32) & 0xffff;
124 double _drand48(void)
128 (void) _erand48_r(__libc_drand48_data.__x, &__libc_drand48_data,
134 void _srand(unsigned int seed)
141 const long a = 16807;
142 const long m = 2147483647;
143 const long q = 127773; /* (m/a) */
144 const long r = 2836; /* (m%a) */
159 _seed = (int) (s & RAND_MAX);
164 int _rand_r(unsigned int *pseed)
166 const long a = 16807;
167 const long m = 2147483647;
168 const long q = 127773; /* (m/a) */
169 const long r = 2836; /* (m%a) */
184 return (int) (s & RAND_MAX);
189 #define rand_r _rand_r
190 #define drand48 _drand48
194 static double custom_random(Generator generator, long int *seed)
201 return (double) rand_r((unsigned int *) seed) / RAND_MAX;
203 XBT_INFO("Seen RNGSTREAM");
210 /* Generate numbers between min and max with a given mean and standard deviation */
211 double random_generate(random_data_t random)
214 double alpha, beta, gamma;
215 double U1, U2, V, W, X;
220 if (random->std == 0)
221 return random->mean * (random->max - random->min) + random->min;
223 a = random->mean * (random->mean * (1 - random->mean) /
224 (random->std * random->std) - 1);
226 random->mean) * (random->mean * (1 -
227 random->mean) / (random->std *
231 if (a <= 1. || b <= 1.)
232 beta = ((1. / a) > (1. / b)) ? (1. / a) : (1. / b);
234 beta = sqrt((alpha - 2.) / (2. * a * b - alpha));
235 gamma = a + 1. / beta;
238 /* Random generation for the Beta distribution based on
239 * R. C. H. Cheng (1978). Generating beta variates with nonintegral shape parameters. _Communications of the ACM_, *21*, 317-322.
240 * It is good for speed because it does not call math functions many times and respect the 4 given constraints
242 U1 = custom_random(random->generator, &(random->seed));
243 U2 = custom_random(random->generator, &(random->seed));
245 V = beta * log(U1 / (1 - U1));
247 } while (alpha * log(alpha / (b + W)) + gamma * V - log(4) <
252 return X * (random->max - random->min) + random->min;
255 random_data_t random_new(Generator generator, long int seed,
256 double min, double max, double mean, double std)
258 random_data_t random = xbt_new0(s_random_data_t, 1);
260 random->generator = generator;
265 /* Check user stupidities */
267 THROWF(arg_error, 0, "random->max < random->min (%f < %f)", max, min);
269 THROWF(arg_error, 0, "random->mean < random->min (%f < %f)", mean,
272 THROWF(arg_error, 0, "random->mean > random->max (%f > %f)", mean,
275 /* normalize the mean and standard deviation before storing */
276 random->mean = (mean - min) / (max - min);
277 random->std = std / (max - min);
279 if (random->mean * (1 - random->mean) < random->std * random->std)
280 THROWF(arg_error, 0, "Invalid mean and standard deviation (%f and %f)",
281 random->mean, random->std);