int a {::rand()};

int b {::rand()};

int transform() const {

return a*a + 2*a*b + b*b;

}

std::vector<int> data;

for(int i=0; i<40000000; ++i) {

data.push_back(::rand());

}

std::cout << "Benchmark: reduce" << std::endl;

// sequential method

auto sbeg = std::chrono::steady_clock::now();

auto smin = std::numeric_limits<int>::max();

for(auto& d : data) {

smin = std::min(smin, d);

}

auto send = std::chrono::steady_clock::now();

std::cout << "[sequential] reduce: "

<< std::chrono::duration_cast<std::chrono::milliseconds>(send - sbeg).count()

<< " ms\n";

// taskflow

auto tbeg = std::chrono::steady_clock::now();

tf::Taskflow tf;

auto tmin = std::numeric_limits<int>::max();

tf.reduce(data.begin(), data.end(), tmin, [] (const auto& l, const auto& r) {

return std::min(l, r);

});

tf.wait_for_all();

auto tend = std::chrono::steady_clock::now();

std::cout << "[taskflow] reduce: "

<< std::chrono::duration_cast<std::chrono::milliseconds>(tend - tbeg).count()

<< " ms\n";

// assertion

assert(tmin == smin);

std::cout << "Benchmark: transform_reduce" << std::endl;

std::vector<Data> data(40000000);

// sequential method

auto sbeg = std::chrono::steady_clock::now();

auto smin = std::numeric_limits<int>::max();

for(auto& d : data) {

smin = std::min(smin, d.transform());

}

auto send = std::chrono::steady_clock::now();

std::cout << "[sequential] transform_reduce "

<< std::chrono::duration_cast<std::chrono::milliseconds>(send - sbeg).count()

<< " ms\n";

// taskflow

auto tbeg = std::chrono::steady_clock::now();

tf::Taskflow tf;

auto tmin = std::numeric_limits<int>::max();

tf.transform_reduce(data.begin(), data.end(), tmin,

[] (int l, int r) { return std::min(l, r); },

[] (const Data& d) { return d.transform(); }

);

tf.wait_for_all();

auto tend = std::chrono::steady_clock::now();

std::cout << "[taskflow] transform_reduce "

<< std::chrono::duration_cast<std::chrono::milliseconds>(tend - tbeg).count()

<< " ms\n";

// assertion

assert(tmin == smin);

if(argc != 2) {

std::cerr << "usage: ./reduce [reduce|transform_reduce]" << std::endl;

std::exit(EXIT_FAILURE);

}

if(std::string_view method(argv[1]); method == "reduce") {

reduce();

}

else if(method == "transform_reduce") {

transform_reduce();

}

else {

std::cerr << "invalid method " << method.data() << std::endl;

std::exit(EXIT_FAILURE);

}

return 0;