Add exapmle for std::latch

Author: Lisa Julia Nebel

.gitignore

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+assemble_teams_using_latch

Makefile

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+# Compiler settings and get all binaries
+CXX = g++
+CXXFLAGS = -std=c++20 -Wall
+SRC = $(wildcard *.cc)
+BIN = $(SRC:.cc=)
+
+# Rules
+default: assemble_teams_using_latch 
+
+assemble_teams_using_latch: assemble_teams_using_latch.cc
+	$(CXX) $(CXXFLAGS) -o assemble_teams_using_latch assemble_teams_using_latch.cc
+clean:
+	@$(RM) $(BIN)
+
+
+# Declare that the targets default and clean are not actual files
+.PHONY: default clean

assemble_teams_using_latch.cc

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+#include <algorithm>
+#include <chrono>
+#include <iostream>
+#include <latch>
+#include <memory>
+#include <random>
+#include <thread>
+#include <vector>
+
+std::random_device rd;   // Non-deterministic random number generator
+std::mt19937 gen(rd());  // Seed the generator
+std::uniform_int_distribution<> dist(1, 5);  // Distribution for random wait time
+
+class TeamManager {
+public:
+    TeamManager(int team_size, int number_of_teams)
+        : team_size_(team_size)
+        , number_of_teams_(number_of_teams)
+    {
+        latches_.reserve(number_of_teams_);
+        for (int i = 0; i < number_of_teams_; ++i) {
+            auto latch = std::make_shared<std::latch>(team_size_);
+            latches_.push_back(latch);
+        }
+    }
+
+    void member_arrives(int member_id, int team_id) {
+        // Assign member to the chosen team, starting from team 1 to 4
+        std::cout << "Member " << member_id << " is assigned to Team " << team_id + 1 << "." << std::endl;
+        latches_[team_id]->count_down();
+    }
+
+    void wait_for_teams() {
+        std::for_each(latches_.begin(), latches_.end(), [](const auto& latch) { latch->wait(); });
+    }
+
+private:
+    int team_size_;
+    int number_of_teams_;
+    std::vector<std::shared_ptr<std::latch>> latches_;
+};
+
+void member_thread(TeamManager& manager, int member_id, int team_id) {
+    auto waitingTime = dist(gen);
+    std::cout << "Member " << member_id << " is on the way... that will take " << waitingTime << " s." << std::endl;
+    // Simulate random travel time
+    std::this_thread::sleep_for(std::chrono::seconds(waitingTime));
+    
+    manager.member_arrives(member_id, team_id);
+}
+
+int main() {
+    const int team_size = 3;        // Number of members required per team
+    const int number_of_teams = 4;  // Number of teams
+
+    TeamManager manager(team_size, number_of_teams);
+
+    std::cout << "Calling the team members..." << std::endl;
+
+    // Create threads for members arriving
+    std::vector<std::thread> members;
+    for (int i = 0; i < team_size * number_of_teams; ++i) {
+        members.emplace_back(member_thread, std::ref(manager), i + 1, i % number_of_teams);
+    }
+
+    std::cout << "Waiting for all team members to arrive and get assigned..." << std::endl;
+    // Manager starts to wait, since now the "members are in the pipeline"
+    manager.wait_for_teams();
+
+    // Join all member threads, i.e. start the actual arrival process, concurrently for all members
+    for (auto& member : members) {
+        member.join();
+    }
+    
+    std::cout << "All teams are ready to play! The game begins!" << std::endl;
+
+    return 0;
+}