@lirtosiast/

# L'ecuyers RNG analysis

## No description

Files
• main.cpp
main.cpp
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```
```#include <iostream>
#include <cmath>
#include <iomanip>
#include <chrono>
//our goal is to find random seeds that produce small values

using namespace std;

const long mod1  = 2147483563;
const long mod2  = 2147483399;
const long mult1 = 40014;
const long mult2 = 40692;
const long mult1sq = mult1 * mult1; // 1601120196

const long MAX_SEED = 1000000000 - 1;
const long ITERATIONS = 10;
long seed1,seed2;

void Seed(int n){
if(n<0) //Perform an abs
n = -n;
if(n==0){
seed1 = 12345; //Gotta love these seed values!
seed2 = 67890;
} else {
seed1 = (mult1*n)%mod1;
seed2 = n%mod2;
}
}

long generate_long() {
seed1  = (seed1*mult1) % mod1;
seed2  = (seed2*mult2) % mod2;
return seed1-seed2;
}

int generate_first(long s) {
int x1 = (s*mult1sq) % mod1;
int x2 = (s*mult2) % mod2;
return x1 - x2;
}

double convert_01(long value) {
double ret = (double) value / (double) mod1;
if(ret < 0) ret += 1;
return ret;
}

double Generate(){
return convert_01(generate_long());
}

int main(){

auto start = chrono::high_resolution_clock::now();
long s;
long inc1 = 0;
long inc2 = 0;

for(long s = 1; s < MAX_SEED; s ++) {

Seed(s);
for(int i = 1; i < ITERATIONS; i++) {

int value = generate_long();
if(abs(value) < 5) {
cout << "seed = " << s <<
", i = " << i <<
", intvalue = " << value <<
", floatvalue = " << setprecision(20) << convert_01(value) << endl;
}
}
}

auto elapsed = chrono::high_resolution_clock::now() - start;

double seconds = ((double) std::chrono::duration_cast<std::chrono::microseconds>(elapsed).count()) / 1000000;

cout << "Time: " << seconds;

}

/*

Success with s = 0, x = 0
Success with s = 143697972, x = 7
Success with s = 144839781, x = -9
Success with s = 196164532, x = 0
Success with s = 339862504, x = 7
Success with s = 341004313, x = -9
Success with s = 392329064, x = 0
Success with s = 537168845, x = -9
Success with s = 588493596, x = 0
Success with s = 733333377, x = -9
Success with s = 784658128, x = 0
Success with s = 929497909, x = -9
Success with s = 980822660, x = 0
Time to 5*10^8: 28.4657   */```