2 #include "surf/random_mgr.h"
3 #include "xbt/sysdep.h"
6 static double drand48(void)
13 static double custom_random(int generator){
16 case DRAND48:return drand48();
17 case RAND: return (double)rand()/RAND_MAX;
18 default: return drand48();
22 /* Generate numbers between min and max with a given mean and standard deviation */
23 float random_generate(random_data_t random){
26 if (random == NULL) return 0.0f;
29 /* Apply the polar form of the Box-Muller Transform to map the two uniform random numbers to a pair of numbers from a normal distribution.
30 It is good for speed because it does not call math functions many times. Another way would be to simply:
31 y1 = sqrt( - 2 * log(x1) ) * cos( 2 * pi * x2 )
34 x1 = 2.0 * custom_random(random->generator) - 1.0;
35 x2 = 2.0 * custom_random(random->generator) - 1.0;
36 w = x1 * x1 + x2 * x2;
39 w = sqrt( (-2.0 * log( w ) ) / w );
42 /* Multiply the Box-Muller value by the standard deviation and add the mean */
43 y = y * random->stdDeviation + random->mean;
44 } while (!(random->min <= y && y <= random->max));
49 random_data_t random_new(int generator, int min, int max, int mean, int stdDeviation){
50 random_data_t random = xbt_new0(s_random_data_t, 1);
51 random->generator = generator;
55 random->stdDeviation = stdDeviation;