CS202 Thread and Space Ship Operator Example

#include <iostream>
#include <iomanip>
#include <compare>
#include <thread>
#include <mutex>
#include <vector>
#include <chrono>
#include <string>

struct SpaceShip {
    int i;

    std::strong_ordering operator<=>(SpaceShip const& rhs) {
        return i <=> rhs.i;
    }
};

void spaceship(int a, int b) {
    std::cout << "a: " << a << "\n";
    std::cout << "b: " << b << "\n";
    auto result = (a <=> b);
    if (result < 0) std::cout << "a <=> b is negative\n";
    if (result > 0) std::cout << "a <=> b is positive\n";
    if (result == 0) std::cout << "a <=> b is equivalent\n";
}

std::mutex cout_mutex;
void print(int taskID, int i, int j) {
    const std::lock_guard<std::mutex> lock(cout_mutex);
    std::cout << "Task i " << taskID << " i: " << i << " " << "j: " << j << "\n";
}

void hardTask(int taskID) {
    constexpr int items = 100;
    for (int i = 0; i < items; i++) {
        for (int j = 0; j < items; j++) {
            if (rand() % 1000 < 2)
                print(taskID, i, j);
            std::sin(i * j);
        }
    }
    const std::lock_guard<std::mutex> lock(cout_mutex);
    std::cout << "Task " << taskID << " done\n";
}

void supercomputer() {
    std::vector<std::thread> threadPool;
    for (int i = 0; i < 32; i++)
        threadPool.push_back(std::thread(hardTask, i));

    for (auto& t : threadPool) {
        t.join();
    }
}

int game_done = 0;
std::string message;
std::mutex game_mutex;

void display_thread() {
    while (!game_done) {
        if (!message.empty()) {
            std::cout << message << "\n";
            const std::lock_guard<std::mutex> lock(game_mutex);
            message.clear();
        }
        using namespace std::chrono_literals;
        std::this_thread::sleep_for(1s);
    }
}

void input_thread() {
    while (!game_done) {
        std::string input;
        std::getline(std::cin, input);
        if (input == "quit") {
            const std::lock_guard<std::mutex> lock(game_mutex);
            game_done = 1;
        }
        else if (!input.empty()) {
            const std::lock_guard<std::mutex> lock(game_mutex);
            message = input;
        }
    }
}

void game() {
    std::thread display(display_thread);
    std::thread input(input_thread);
    input.join();
    display.join();
}

int main() {
    //spaceship(1, 3);
    //spaceship(3, 1);
    //spaceship(1, 1);
    //spaceship(0, 0);

    //supercomputer();

    game();

    return 0;
}