Countdown Barrier Coordination Report

Count arrivals down to a release barrier and report whether it has opened.

Countdown Barrier Coordination Report

countdown_barrier_coordination_report.cpp

#include <atomic>
#include <iostream>
#include <string>

int main() {
    int arrivals = ;
    const int parties = 3;
    std::atomic<int> remaining{parties};
    int signaled = 0;

    for (int i = 0; i < arrivals; ++i) {
        if (remaining.load() > 0) {
            remaining.fetch_sub(1);
            signaled += 1;
        }
    }

    int left = remaining.load();

    std::string status;
    if (signaled == 0) {
        status = "waiting";
    } else if (left > 0) {
        status = "partial";
    } else {
        status = "released";
    }

    std::cout << "arrivals=" << arrivals
              << " signaled=" << signaled
              << " remaining=" << left
              << " " << status << std::endl;
    return 0;
}

#include <atomic>
#include <iostream>
#include <string>

int main() {
    int arrivals = ;
    const int parties = 3;
    std::atomic<int> remaining{parties};
    int signaled = 0;

    for (int i = 0; i < arrivals; ++i) {
        if (remaining.load() > 0) {
            remaining.fetch_sub(1);
            signaled += 1;
        }
    }

    int left = remaining.load();

    std::string status;
    if (signaled == 0) {
        status = "waiting";
    } else if (left > 0) {
        status = "partial";
    } else {
        status = "released";
    }

    std::cout << "arrivals=" << arrivals
              << " signaled=" << signaled
              << " remaining=" << left
              << " " << status << std::endl;
    return 0;
}

#include <atomic>
#include <iostream>
#include <string>

int main() {
    int arrivals = ;
    const int parties = 3;
    std::atomic<int> remaining{parties};
    int signaled = 0;

    for (int i = 0; i < arrivals; ++i) {
        if (remaining.load() > 0) {
            remaining.fetch_sub(1);
            signaled += 1;
        }
    }

    int left = remaining.load();

    std::string status;
    if (signaled == 0) {
        status = "waiting";
    } else if (left > 0) {
        status = "partial";
    } else {
        status = "released";
    }

    std::cout << "arrivals=" << arrivals
              << " signaled=" << signaled
              << " remaining=" << left
              << " " << status << std::endl;
    return 0;
}

countdown to release A countdown barrier opens only after a fixed number of parties arrive. A `std::atomic<int>` remaining counter starts at the party count, and each arrival uses `fetch_sub` to drop it by one while it is still positive, so the counter never goes below zero and the number of recorded signals is exact. The single deterministic pass means the report can state how many arrivals were signaled and how many remain, labeling the barrier waiting before the first arrival, partial while some parties are missing, or released once the count reaches zero.