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#ifndef UTIL_RANDOM_H
#define UTIL_RANDOM_H
#include <stdint.h>
#include <sys/time.h>
#include <time.h>
// Taken from
// http://software.intel.com/en-us/articles/fast-random-number-generator-on-the-intel-pentiumr-4-processor/
namespace util
{
namespace internal
{
inline uint32_t time_seed()
{
timeval tv;
gettimeofday(&tv, NULL);
return tv.tv_sec ^ tv.tv_usec;
}
inline int_fast16_t rand(uint32_t setseed)
{
static uint32_t mySeed = (uint32_t)(-1);
if (setseed != (uint32_t)(-2))
mySeed = setseed;
if (mySeed == (uint32_t)(-1))
mySeed = time_seed();
mySeed = 214013 * mySeed + 2531011;
return (mySeed >> 16) & 0x7FFF;
}
}
inline int_fast16_t urand()
{
return internal::rand(-2);
}
inline int_fast16_t urandn(int32_t n)
{
return urand() % n;
}
inline void usrand(uint64_t seed)
{
internal::rand(seed);
}
class Random
{
private:
static uint32_t auto_seed(uint32_t setSeed);
uint32_t mySeed;
public:
Random();
Random(uint64_t seed);
int_fast16_t rand();
int_fast16_t rand(int32_t n);
int_fast16_t operator()();
int_fast16_t operator()(int32_t n);
void srand(uint64_t seed);
};
inline uint32_t Random::auto_seed(uint32_t setSeed)
{
static uint32_t internalSeed = 0;
if (setSeed == 0)
return internalSeed;
uint32_t result = internalSeed;
internalSeed = setSeed;
return result;
}
inline Random::Random()
{
if (auto_seed(0) == 0)
auto_seed(internal::time_seed());
mySeed = auto_seed(0);
auto_seed((rand() << 16) ^ (rand()) ^ internal::time_seed());
}
inline Random::Random(uint64_t seed)
: mySeed(seed) { }
inline void Random::srand(uint64_t seed)
{
mySeed = seed;
}
inline int_fast16_t Random::rand()
{
mySeed = 214013 * mySeed + 2531011;
return (mySeed >> 16) & 0x7FFF;
}
inline int_fast16_t Random::rand(int32_t n)
{
return rand() % n;
}
inline int_fast16_t Random::operator()()
{
return rand();
}
inline int_fast16_t Random::operator()(int32_t n)
{
return rand(n);
}
} // namespace util
#endif // UTIL_RANDOM_H