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random.cpp
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random.cpp
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#include <random>
#include "threads.h"
#include <time.h>
#include "constants.h"
#include "vec3.h"
#include "vec2.h"
#include "main/references.h"
#include "os/driver.h"
#include "random.h"
#if defined(_MSC_VER)
#include <intrin.h>
#define GET_MSB(var, x) do{ unsigned long _index_; _BitScanReverse(&_index_, x); var = _index_ + 1; } while(false)
#elif defined(__GNUC__)
#define GET_MSB(var, x) do { var = (32 - __builtin_clz(x)); } while(false)
#else
unsigned _get_msb(unsigned v) {
unsigned index = 0;
while((1 << index) <= v)
++index;
return index;
}
#define GET_MSB(var, x) do { var = _get_msb(x); } while(false)
#endif
Threaded(std::mt19937*) engine;
void seed(unsigned long seed);
void initRandomizer() {
engine = new std::mt19937();
seed((unsigned long)time(0) ^ (unsigned long)threads::getThreadID());
}
void freeRandomizer() {
delete engine;
}
void seed(unsigned long seed) {
engine->seed(seed);
}
unsigned sysRandomi() {
unsigned ret = 0;
if(!devices.driver->systemRandom((unsigned char*)&ret, 4)) {
if(engine)
ret = (unsigned)randomi();
else {
initRandomizer();
ret = (unsigned)randomi();
freeRandomizer();
}
}
return ret;
}
double randomd() {
//Choose random numbers until we don't get max
unsigned m = engine->max();
unsigned r;
do {
r = (*engine)();
} while(r == m);
return (double)r / (double)m;
}
double randomd(double min, double max) {
return randomd() * (max - min) + min;
}
double normald(double min, double max, int steps) {
double sum = 0;
for(int i = 0; i < steps; ++i)
sum += randomd();
return min + (max-min)*sum/(double)steps;
}
float randomf() {
return (float)randomd();
}
float randomf(float min, float max) {
return (float)(randomd() * (double)(max - min)) + min;
}
unsigned randomi() {
return (*engine)();
}
int randomi(int min, int max) {
unsigned range = (unsigned)max - (unsigned)min;
if(range == 0)
return min;
unsigned msb;
GET_MSB(msb, range);
unsigned mask = 0xffffffff >> (32 - msb);
//Choose uniformly distributed values until one falls into our range
//Worst case scenario is the possible values is split in half (+1), so it will still resolve quickly
unsigned r;
do {
r = (unsigned)((*engine)());
} while((r & mask) > range);
return min + (r & mask);
}
vec3d random3d(double radius) {
double theta = randomd(0, twopi);
double u = randomd(-1.0, 1.0);
double s = sqrt(1.0-(u*u));
vec3d out;
out.x = s * cos(theta) * radius;
out.y = s * sin(theta) * radius;
out.z = u * radius;
return out;
}
vec3d random3d(double minRadius, double maxRadius) {
return random3d(minRadius + (maxRadius - minRadius) * sqrt(randomd()));
}
vec2d random2d(double radius) {
double theta = randomd(0, twopi);
return vec2d(radius * cos(theta), radius * sin(theta));
}
vec2d random2d(double minRadius, double maxRadius) {
return random2d(minRadius + (maxRadius - minRadius) * sqrt(randomd()));
}
class MersenneEngine : public RandomEngine {
std::mt19937 rnd;
public:
void seed(unsigned initial) {
rnd.seed((unsigned long)initial);
}
unsigned randomi() {
return rnd();
}
unsigned randomi(unsigned min, unsigned max) {
unsigned range = (unsigned)max - (unsigned)min;
if(range == 0)
return min;
unsigned msb;
GET_MSB(msb, range);
unsigned mask = 0xffffffff >> (32 - msb);
//Choose uniformly distributed values until one falls into our range
//Worst case scenario is the possible values is split in half (+1), so it will still resolve quickly
unsigned r;
do {
r = (unsigned)(rnd());
} while((r & mask) > range);
return min + (r & mask);
}
double randomd() {
unsigned m = rnd.max();
unsigned r;
do {
r = rnd();
} while(r == m);
return (double)r / (double)m;
}
double randomd(double min, double max) {
return (randomd() * (max - min)) + min;
}
};
RandomEngine* RandomEngine::makeMersenne(unsigned seed) {
auto* engine = new MersenneEngine();
engine->seed(seed);
return engine;
}

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