1 #include "surf/random_mgr.h"
2 #include "xbt/sysdep.h"
6 static unsigned int _seed = 2147483647;
8 typedef unsigned __int64 uint64_t;
9 typedef unsigned int uint32_t;
12 unsigned short int __x[3]; /* Current state. */
13 unsigned short int __old_x[3]; /* Old state. */
14 unsigned short int __c; /* Additive const. in congruential formula. */
15 unsigned short int __init; /* Flag for initializing. */
16 unsigned long long int __a; /* Factor in congruential formula. */
19 static struct drand48_data __libc_drand48_data = { 0 };
21 union ieee754_double {
24 /* This is the IEEE 754 double-precision format. */
26 /* Together these comprise the mantissa. */
27 unsigned int mantissa1:32;
28 unsigned int mantissa0:20;
29 unsigned int exponent:11;
30 unsigned int negative:1;
34 /* This format makes it easier to see if a NaN is a signalling NaN. */
36 /* Together these comprise the mantissa. */
37 unsigned int mantissa1:32;
38 unsigned int mantissa0:19;
39 unsigned int quiet_nan:1;
40 unsigned int exponent:11;
41 unsigned int negative:1;
46 #define IEEE754_DOUBLE_BIAS 0x3ff /* Added to exponent. */
51 _drand48_iterate(unsigned short int xsubi[3], struct drand48_data *buffer);
54 _erand48_r(unsigned short int xsubi[3], struct drand48_data *buffer,
59 _erand48_r(unsigned short int xsubi[3], struct drand48_data *buffer,
62 union ieee754_double temp;
64 /* Compute next state. */
65 if (_drand48_iterate(xsubi, buffer) < 0)
68 /* Construct a positive double with the 48 random bits distributed over
69 its fractional part so the resulting FP number is [0.0,1.0). */
71 temp.ieee.negative = 0;
72 temp.ieee.exponent = IEEE754_DOUBLE_BIAS;
73 temp.ieee.mantissa0 = (xsubi[2] << 4) | (xsubi[1] >> 12);
74 temp.ieee.mantissa1 = ((xsubi[1] & 0xfff) << 20) | (xsubi[0] << 4);
76 /* Please note the lower 4 bits of mantissa1 are always 0. */
77 *result = temp.d - 1.0;
82 int _drand48_iterate(unsigned short int xsubi[3], struct drand48_data *buffer)
87 /* Initialize buffer, if not yet done. */
89 if (buffer->__init == 0) {
90 buffer->__a = 0x5deece66dull;
95 /* Do the real work. We choose a data type which contains at least
96 48 bits. Because we compute the modulus it does not care how
97 many bits really are computed. */
99 X = (uint64_t) xsubi[2] << 32 | (uint32_t) xsubi[1] << 16 | xsubi[0];
101 result = X * buffer->__a + buffer->__c;
104 xsubi[0] = result & 0xffff;
105 xsubi[1] = (result >> 16) & 0xffff;
106 xsubi[2] = (result >> 32) & 0xffff;
112 double _drand48(void)
116 (void) _erand48_r(__libc_drand48_data.__x, &__libc_drand48_data, &result);
121 void _srand(unsigned int seed)
128 const long a = 16807;
129 const long m = 2147483647;
130 const long q = 127773; /* (m/a) */
131 const long r = 2836; /* (m%a) */
146 _seed = (int) (s & RAND_MAX);
151 int _rand_r(unsigned int *pseed)
153 const long a = 16807;
154 const long m = 2147483647;
155 const long q = 127773; /* (m/a) */
156 const long r = 2836; /* (m%a) */
171 return (int) (s & RAND_MAX);
176 #define rand_r _rand_r
177 #define drand48 _drand48
181 static double custom_random(Generator generator, long int *seed)
188 return (double) rand_r((unsigned int *) seed) / RAND_MAX;
194 /* Generate numbers between min and max with a given mean and standard deviation */
195 double random_generate(random_data_t random)
198 double alpha, beta, gamma;
199 double U1, U2, V, W, X;
204 if (random->std == 0)
205 return random->mean * (random->max - random->min) + random->min;
208 random->mean * (random->mean * (1 - random->mean) /
209 (random->std * random->std) - 1);
212 random->mean) * (random->mean * (1 -
213 random->mean) / (random->std *
217 if (a <= 1. || b <= 1.)
218 beta = ((1. / a) > (1. / b)) ? (1. / a) : (1. / b);
220 beta = sqrt((alpha - 2.) / (2. * a * b - alpha));
221 gamma = a + 1. / beta;
224 /* Random generation for the Beta distribution based on
225 * R. C. H. Cheng (1978). Generating beta variates with nonintegral shape parameters. _Communications of the ACM_, *21*, 317-322.
226 * It is good for speed because it does not call math functions many times and respect the 4 given constraints
228 U1 = custom_random(random->generator, &(random->seed));
229 U2 = custom_random(random->generator, &(random->seed));
231 V = beta * log(U1 / (1 - U1));
233 } while (alpha * log(alpha / (b + W)) + gamma * V - log(4) <
238 return X * (random->max - random->min) + random->min;
241 random_data_t random_new(Generator generator, long int seed,
242 double min, double max, double mean, double std)
244 random_data_t random = xbt_new0(s_random_data_t, 1);
246 random->generator = generator;
251 /* Check user stupidities */
253 THROW2(arg_error, 0, "random->max < random->min (%f < %f)", max, min);
255 THROW2(arg_error, 0, "random->mean < random->min (%f < %f)", mean, min);
257 THROW2(arg_error, 0, "random->mean > random->max (%f > %f)", mean, max);
259 /* normalize the mean and standard deviation before storing */
260 random->mean = (mean - min) / (max - min);
261 random->std = std / (max - min);
263 if (random->mean * (1 - random->mean) < random->std * random->std)
264 THROW2(arg_error, 0, "Invalid mean and standard deviation (%f and %f)",
265 random->mean, random->std);