Thread Local Context

Keep per-thread state with thread_local storage.

thread_local_context.cpp

#include <iostream>
#include <thread>

thread_local int localScore = 0;

void writeLocalScore(int boost, int offset, int* output) {
    localScore = boost + offset;
    *output = localScore;
}

int main() {
    int boost = ;
    int firstScore = 0;
    int secondScore = 0;

    std::thread first(writeLocalScore, boost, 10, &firstScore);
    std::thread second(writeLocalScore, boost, 20, &secondScore);

    first.join();
    second.join();

    int total = firstScore + secondScore;
    std::cout << "boost=" << boost << std::endl;
    std::cout << "total=" << total << std::endl;
    return 0;
}

#include <iostream>
#include <thread>

thread_local int localScore = 0;

void writeLocalScore(int boost, int offset, int* output) {
    localScore = boost + offset;
    *output = localScore;
}

int main() {
    int boost = ;
    int firstScore = 0;
    int secondScore = 0;

    std::thread first(writeLocalScore, boost, 10, &firstScore);
    std::thread second(writeLocalScore, boost, 20, &secondScore);

    first.join();
    second.join();

    int total = firstScore + secondScore;
    std::cout << "boost=" << boost << std::endl;
    std::cout << "total=" << total << std::endl;
    return 0;
}

#include <iostream>
#include <thread>

thread_local int localScore = 0;

void writeLocalScore(int boost, int offset, int* output) {
    localScore = boost + offset;
    *output = localScore;
}

int main() {
    int boost = ;
    int firstScore = 0;
    int secondScore = 0;

    std::thread first(writeLocalScore, boost, 10, &firstScore);
    std::thread second(writeLocalScore, boost, 20, &secondScore);

    first.join();
    second.join();

    int total = firstScore + secondScore;
    std::cout << "boost=" << boost << std::endl;
    std::cout << "total=" << total << std::endl;
    return 0;
}

local Each thread has its own copy of a `thread_local` variable.

merge The main thread merges the values after both worker threads finish.