X-Git-Url: http://info.iut-bm.univ-fcomte.fr/pub/gitweb/simgrid.git/blobdiff_plain/72bdbf81a3dadb1338ae8743d2410842ff04948f..bb6ac9c6781e2639da8957ccf08957974d6ce697:/src/surf/random_mgr.c diff --git a/src/surf/random_mgr.c b/src/surf/random_mgr.c index 6249e33f47..90d0b93ef3 100644 --- a/src/surf/random_mgr.c +++ b/src/surf/random_mgr.c @@ -1,57 +1,263 @@ - #include "surf/random_mgr.h" #include "xbt/sysdep.h" #ifdef WIN32 -static double drand48(void) + +static unsigned int _seed = 2147483647; + +typedef unsigned __int64 uint64_t; +typedef unsigned int uint32_t; + +struct drand48_data +{ + unsigned short int __x[3]; /* Current state. */ + unsigned short int __old_x[3]; /* Old state. */ + unsigned short int __c; /* Additive const. in congruential formula. */ + unsigned short int __init; /* Flag for initializing. */ + unsigned long long int __a; /* Factor in congruential formula. */ +}; + +static struct drand48_data __libc_drand48_data = {0}; + +union ieee754_double + { + double d; + + /* This is the IEEE 754 double-precision format. */ + struct + { + /* Together these comprise the mantissa. */ + unsigned int mantissa1:32; + unsigned int mantissa0:20; + unsigned int exponent:11; + unsigned int negative:1; + /* Little endian. */ + } ieee; + + /* This format makes it easier to see if a NaN is a signalling NaN. */ + struct + { + /* Together these comprise the mantissa. */ + unsigned int mantissa1:32; + unsigned int mantissa0:19; + unsigned int quiet_nan:1; + unsigned int exponent:11; + unsigned int negative:1; + + } ieee_nan; +}; + +#define IEEE754_DOUBLE_BIAS 0x3ff /* Added to exponent. */ + +double +drand48 (void); + +int +_drand48_iterate (unsigned short int xsubi[3], struct drand48_data *buffer); + +int +_erand48_r (unsigned short int xsubi[3], struct drand48_data *buffer, double *result); + + +int +_erand48_r (unsigned short int xsubi[3], struct drand48_data *buffer, double *result) +{ + union ieee754_double temp; + + /* Compute next state. */ + if (_drand48_iterate(xsubi, buffer) < 0) + return -1; + + /* Construct a positive double with the 48 random bits distributed over + its fractional part so the resulting FP number is [0.0,1.0). */ + + temp.ieee.negative = 0; + temp.ieee.exponent = IEEE754_DOUBLE_BIAS; + temp.ieee.mantissa0 = (xsubi[2] << 4) | (xsubi[1] >> 12); + temp.ieee.mantissa1 = ((xsubi[1] & 0xfff) << 20) | (xsubi[0] << 4); + + /* Please note the lower 4 bits of mantissa1 are always 0. */ + *result = temp.d - 1.0; + + return 0; +} + +int +_drand48_iterate (unsigned short int xsubi[3], struct drand48_data *buffer) +{ + uint64_t X; + uint64_t result; + + /* Initialize buffer, if not yet done. */ + + if(buffer->__init == 0) + { + buffer->__a = 0x5deece66dull; + buffer->__c = 0xb; + buffer->__init = 1; + } + + /* Do the real work. We choose a data type which contains at least + 48 bits. Because we compute the modulus it does not care how + many bits really are computed. */ + + X = (uint64_t) xsubi[2] << 32 | (uint32_t) xsubi[1] << 16 | xsubi[0]; + + result = X * buffer->__a + buffer->__c; + + + xsubi[0] = result & 0xffff; + xsubi[1] = (result >> 16) & 0xffff; + xsubi[2] = (result >> 32) & 0xffff; + + return 0; +} + + +double +_drand48 (void) +{ + double result; + + (void) _erand48_r (__libc_drand48_data.__x, &__libc_drand48_data, &result); + + return result; + } + +void +_srand(unsigned int seed) +{ + _seed = seed; +} + +int +_rand(void) { - return rand()/(double)RAND_MAX; + const long a = 16807; + const long m = 2147483647; + const long q = 127773; /* (m/a) */ + const long r = 2836; /* (m%a) */ + + long lo, k, s; + + s = (long)_seed; + + k = (long)(s/q); + + lo = (s - q * k); + + s = a * lo -r * k; + + if(s <= 0) + s += m; + + _seed = (int)(s & RAND_MAX); + + return _seed; } + +int +_rand_r(unsigned int* pseed) +{ + const long a = 16807; + const long m = 2147483647; + const long q = 127773; /* (m/a) */ + const long r = 2836; /* (m%a) */ + + long lo, k, s; + + s = (long)*pseed; + + k = (long)(s/q); + + lo = (s - q * k); + + s = a * lo -r * k; + + if(s <= 0) + s += m; + + return (int)(s & RAND_MAX); + +} + + +#define rand_r _rand_r +#define drand48 _drand48 + #endif -static double custom_random(int generator){ +static double custom_random(Generator generator, long int *seed){ switch(generator) { - - case DRAND48:return drand48(); - case RAND: return (double)rand()/RAND_MAX; - default: return drand48(); + + case DRAND48: + return drand48(); + case RAND: + return (double)rand_r((unsigned int*)seed)/RAND_MAX; + default: + return drand48(); } } /* Generate numbers between min and max with a given mean and standard deviation */ -float random_generate(random_data_t random){ - float x1, x2, w, y; - - if (random == NULL) return 0.0f; +double random_generate(random_data_t random) { + double a, b; + double alpha, beta, gamma; + double U1, U2, V, W, X; + + if (random == NULL) return 0.0f; + + a = random->mean * ( random->mean * (1 - random->mean) / (random->std*random->std) - 1 ); + b = (1 - random->mean) * ( random->mean * (1 - random->mean) / (random->std*random->std) - 1 ); + + alpha = a + b; + if (a <= 1. || b <= 1.) + beta = ((1./a)>(1./b))?(1./a):(1./b); + else + beta = sqrt ((alpha-2.) / (2.*a*b - alpha)); + gamma = a + 1./beta; do { - /* 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. - It is good for speed because it does not call math functions many times. Another way would be to simply: - y1 = sqrt( - 2 * log(x1) ) * cos( 2 * pi * x2 ) - */ - do { - x1 = 2.0 * custom_random(random->generator) - 1.0; - x2 = 2.0 * custom_random(random->generator) - 1.0; - w = x1 * x1 + x2 * x2; - } while ( w >= 1.0 ); + /* Random generation for the Beta distribution based on + * R. C. H. Cheng (1978). Generating beta variates with nonintegral shape parameters. _Communications of the ACM_, *21*, 317-322. + * It is good for speed because it does not call math functions many times and respect the 4 given constraints + */ + U1 = custom_random(random->generator,&(random->seed)); + U2 = custom_random(random->generator,&(random->seed)); - w = sqrt( (-2.0 * log( w ) ) / w ); - y = x1 * w; + V = beta * log(U1/(1-U1)); + W = a * exp(V); + } while (alpha * log(alpha/(b + W)) + gamma*V - log(4) < log(U1*U1*U2)); - /* Multiply the Box-Muller value by the standard deviation and add the mean */ - y = y * random->stdDeviation + random->mean; - } while (!(random->min <= y && y <= random->max)); + X = W / (b + W); - return y; + return X * (random->max - random->min) + random->min; } -random_data_t random_new(int generator, int min, int max, int mean, int stdDeviation){ +random_data_t random_new(Generator generator, long int seed, + double min, double max, + double mean, double std){ random_data_t random = xbt_new0(s_random_data_t, 1); + random->generator = generator; + random->seed = seed; random->min = min; random->max = max; - random->mean = mean; - random->stdDeviation = stdDeviation; + + /* Check user stupidities */ + if (max < min) + THROW2(arg_error,0,"random->max < random->min (%f < %f)",max, min); + if (mean < min) + THROW2(arg_error,0,"random->mean < random->min (%f < %f)",mean, min); + if (mean > max) + THROW2(arg_error,0,"random->mean > random->max (%f > %f)",mean, max); + + /* normalize the mean and standard deviation before storing */ + random->mean = (mean - min) / (max - min); + random->std = std / (max - min); + + if (random->mean * (1-random->mean) < random->std*random->std) + THROW2(arg_error,0,"Invalid mean and standard deviation (%f and %f)",random->mean, random->std); + return random; } -