mt19937.cpp

#include <iostream>
#include <fstream>
#include <array>
#include <random>
// more specifically this will be mt19937

// constant f value used for 32 but mt19937
#define f 1812433253



std::array<uint32_t,624> mt19937_init(uint32_t seed){

    std::array<uint32_t,624> state;

    state[0] = seed;

    for(int i=1; i<624; i++){
        state[i]= f*(state[i-1] ^ (state[i-1] >> 30)) + i;
    }

    return state;
}

std::array<uint32_t,624> mt19937_twist(std::array<uint32_t,624> state){

    std::array<uint32_t,624> newstate;

    for(int i=0; i<624; i++){
        uint32_t oldstate = state[i];

        // concating the MSB and LSB from next
        uint32_t x;

        if(i+1<624){
            x = (state[i] & 0x80000000) | (state[(i+1)] & 0x7FFFFFFF);
        }else{
            x = (state[i] & 0x80000000) | (newstate[(i+1)%624] & 0x7FFFFFFF);
        }
        // does the *A part

        if(x&1){
            x = (x>>1) ^ 0x9908B0DFUL;
        }else{
            x=x>>1;
        }

        uint32_t y;
        if(i+397<624){
            y = state[i+397] ^ x;
        }else{
            y = newstate[(i+397) % 624] ^ x;
        }
        newstate[i] = y;
    }

    return newstate;
}

std::array<uint32_t,624> mt19937_temper(std::array<uint32_t,624> state){
    std::array<uint32_t, 624> tempered;

    for(int i=0; i<624; i++){

        uint32_t y = state[i];
        y = y ^ (y >> 11);
        y = y ^ ((y << 7) & 0x9D2C5680UL);
        y = y ^ ((y << 15) & 0xEFC60000UL);
        tempered[i] = y ^ (y >> 18);
    }

    return tempered;
}

class mt19937_generator {
    public: 
        uint32_t seed;
        uint32_t generate() {
            uint32_t generated = random_values[position];
            position++;
            if(position>=624){
                nextblock();
            }
            return generated;
        }
        mt19937_generator(uint32_t genSeed){
            seed = genSeed;
            state = mt19937_init(seed);
            nextblock();
        }
    private:
        std::array<uint32_t,624> state;
        std::array<uint32_t,624> random_values;
        int position;
        // goes to next block of 624 values
        void nextblock() {
            state = mt19937_twist(state);
            random_values = mt19937_temper(state);
            position = 0;
        }
};