//test.cpp

#include <iostream>
#include <thread>
#include <random>
#include "TRandom3.h"
#include "TCanvas.h"
#include "ROOT/RDataFrame.hxx"

/*
struct RandomEngines{
    RandomEngines(){
        //Assuming you have <= 64 cores
        for (int i=0; i<64; i++) engines.push_back( TRandom3( rd() ) );
    }
    std::vector< TRandom3 > engines;

    // for random seeding of several random engines
    std::random_device rd;
};

RandomEngines engines;*/
TRandom3 rg;

double GetRNG() { return rg.Gaus(); }
double GetRNG_threadlocal_engine() { static thread_local TRandom3 r3(std::hash<std::thread::id>{}(std::this_thread::get_id())); /* you can also use rand() as seed instead*/ return r3.Gaus(); }

double GetRNGSlot() { 
    static thread_local TRandom3 r3;
    return r3.Gaus();
}

void test(){
    auto* c1 = new TCanvas("c1", "c1", 1500, 500);
    c1->Divide(3, 1);
    
    ROOT::DisableImplicitMT();
    auto df1 = ROOT::RDataFrame(90000000).Define("x", GetRNG);
    auto h1 = df1.Histo1D({"h1", "single core", 1000, -4, 4}, {"x"});    
    c1->cd(1);
    h1->DrawClone();

    
    ROOT::EnableImplicitMT(16);
    auto df3 = ROOT::RDataFrame(90000000).Define("x", GetRNG);
    auto df4 = ROOT::RDataFrame(90000000).Define("x", GetRNG_threadlocal_engine);
    
    auto h3 = df3.Histo1D({"h3", "single random engine", 1000, -4, 4}, {"x"});
    auto h4 = df4.Histo1D({"h4", "threadlocal engines", 1000, -4, 4}, {"x"});
    
    c1->cd(2);
    h3->DrawClone();
    c1->cd(3);
    h4->DrawClone();
    std::cout<<std::fixed<<std::setprecision(3)<<"Perfect                    : "<<"0.000"<<" +- "<<"1.000"<<std::endl;
    std::cout<<std::fixed<<std::setprecision(3)<<"Single thread              : "<<h1->GetMean()<<" +- "<<h1->GetStdDev()<<std::endl;
    std::cout<<std::fixed<<std::setprecision(3)<<"single random engine   (MT): "<<h3->GetMean()<<" +- "<<h3->GetStdDev()<<std::endl;
    std::cout<<std::fixed<<std::setprecision(3)<<"Threadlocal engines    (MT): "<<h4->GetMean()<<" +- "<<h4->GetStdDev()<<std::endl;   
}