class latch;
(since C++20)The latch class is a downward counter of type std::ptrdiff_t which can be used to synchronize threads. The value of the counter is initialized on creation. Threads may block on the latch until the counter is decremented to zero. There is no possibility to increase or reset the counter, which makes the latch a single-use barrier.
Concurrent invocations of the member functions of std::latch, except for the destructor, do not introduce data races.
counter the internal counter
latch
latch
latch is not assignable
#include <functional>
#include <iostream>
#include <latch>
#include <string>
#include <thread>
struct Job
{
const std::string name;
std::string product{"not worked"};
std::thread action{};
};
int main()
{
Job jobs[]{{"Annika"}, {"Buru"}, {"Chuck"}};
std::latch work_done{std::size(jobs)};
std::latch start_clean_up{1};
auto work = [&](Job& my_job)
{
my_job.product = my_job.name + " worked";
work_done.count_down();
start_clean_up.wait();
my_job.product = my_job.name + " cleaned";
};
std::cout << "Work is starting... ";
for (auto& job : jobs)
job.action = std::thread{work, std::ref(job)};
work_done.wait();
std::cout << "done:\n";
for (auto const& job : jobs)
std::cout << " " << job.product << '\n';
std::cout << "Workers are cleaning up... ";
start_clean_up.count_down();
for (auto& job : jobs)
job.action.join();
std::cout << "done:\n";
for (auto const& job : jobs)
std::cout << " " << job.product << '\n';
}
Output:
Work is starting... done: Annika worked Buru worked Chuck worked Workers are cleaning up... done: Annika cleaned Buru cleaned Chuck cleaned[edit] See also
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