2 #include "surf/random_mgr.h"
3 #include "xbt/sysdep.h"
5 static double custom_random(int generator){
7 case DRAND48: return drand48(); break;
8 case RAND: return (double)rand()/RAND_MAX; break;
9 default: return drand48();
13 /* Generate numbers between min and max with a given mean and standard deviation */
14 float random_generate(random_data_t random){
17 if (random == NULL) return 0.0f;
20 /* 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.
21 It is good for speed because it does not call math functions many times. Another way would be to simply:
22 y1 = sqrt( - 2 * log(x1) ) * cos( 2 * pi * x2 )
25 x1 = 2.0 * custom_random(random->generator) - 1.0;
26 x2 = 2.0 * custom_random(random->generator) - 1.0;
27 w = x1 * x1 + x2 * x2;
30 w = sqrt( (-2.0 * log( w ) ) / w );
33 /* Multiply the Box-Muller value by the standard deviation and add the mean */
34 y = y * random->stdDeviation + random->mean;
35 } while (!(random->min <= y && y <= random->max));
40 random_data_t random_new(int generator, int min, int max, int mean, int stdDeviation){
41 random_data_t random = xbt_new0(s_random_data_t, 1);
42 random->generator = generator;
46 random->stdDeviation = stdDeviation;