diff --git a/random/test_even_distribution.cpp b/random/test_even_distribution.cpp new file mode 100644 index 0000000..71f3f06 --- /dev/null +++ b/random/test_even_distribution.cpp @@ -0,0 +1,105 @@ +#include + +#include +#include + +static uint32_t rprand_state[4] = {0}; +static uint64_t rprand_seed = 0; + +static inline uint32_t my_rotate_left(const uint32_t x, int k) +{ + return (x << k) | (x >> (32 - k)); +} + +uint32_t my_rprand_xoshiro(uint32_t state[4]) +{ + const uint32_t result = my_rotate_left(state[1] * 5, 7) * 9; + const uint32_t t = state[1] << 9; + + state[2] ^= state[0]; + state[3] ^= state[1]; + state[1] ^= state[2]; + state[0] ^= state[3]; + + state[2] ^= t; + + state[3] = my_rotate_left(state[3], 11); + + return result; +} + +uint64_t rprand_splitmix64() +{ + uint64_t z = (rprand_seed += 0x9e3779b97f4a7c15); + z = (z ^ (z >> 30)) * 0xbf58476d1ce4e5b9; + z = (z ^ (z >> 27)) * 0x94d049bb133111eb; + return z ^ (z >> 31); +} + +void setSeed(unsigned long long seed) +{ + rprand_seed = (uint64_t)seed; // Set SplitMix64 seed for further use + + // To generate the Xoshiro128** state, we use SplitMix64 generator first + // We generate 4 pseudo-random 64bit numbers that we combine using their LSB|MSB + rprand_state[0] = (uint32_t)(rprand_splitmix64() & 0xffffffff); + rprand_state[1] = (uint32_t)((rprand_splitmix64() & 0xffffffff00000000) >> 32); + rprand_state[2] = (uint32_t)(rprand_splitmix64() & 0xffffffff); + rprand_state[3] = (uint32_t)((rprand_splitmix64() & 0xffffffff00000000) >> 32); +} + +int getValue(int min, int max) +{ + return my_rprand_xoshiro(rprand_state) % (std::abs(max - min) + 1) + min; +} + +double getFloat() +{ + return my_rprand_xoshiro(rprand_state) / (double)UINT32_MAX; +} + +typedef uint32_t (*func_t)(); +#define N 100 + +static uint32_t Rand7Naive() +{ + return getValue(0, N); +} + +static uint32_t Rand7Float() +{ + return (getFloat() * N); +} + +void Test(func_t rand, std::string name) +{ + uint64_t *buckets = new uint64_t[N]; + for (int i = 0; i < N; i++) + buckets[i] = 0; + + for (int i = 0; i < 100000000; i++) + buckets[rand()]++; + + uint64_t sum = 0; + for (int i = 0; i < N; i++) + sum += buckets[i]; + + printf("%s\n", name.c_str()); + for (int i = 0; i < N; i++) + printf("%d\t%ld\n", i, buckets[i]); + + printf("sum = %ld\n\n", sum); + + delete buckets; +} + +int main(int argc, char const *argv[]) +{ + setSeed((unsigned int)time(NULL)); + + Test(Rand7Naive, "Rand7Naive"); + setSeed((unsigned int)time(NULL)); + Test(Rand7Float, "Rand7Float"); + + return 0; +}