Channel Buffering in Cilk

In Cilk, we can demonstrate buffered channels using the concept of concurrent deques. While Cilk doesn’t have built-in channels like Go, we can simulate similar behavior using Cilk’s parallel constructs and a shared deque data structure.

#include <cilk/cilk.h>
#include <cilk/cilk_api.h>
#include <iostream>
#include <deque>
#include <string>
#include <mutex>

std::deque<std::string> messages;
std::mutex mtx;

void send_message(const std::string& msg) {
    std::lock_guard<std::mutex> lock(mtx);
    messages.push_back(msg);
}

std::string receive_message() {
    std::lock_guard<std::mutex> lock(mtx);
    if (!messages.empty()) {
        std::string msg = messages.front();
        messages.pop_front();
        return msg;
    }
    return "";
}

int main() {
    // Simulate a buffered channel with capacity 2
    const int buffer_size = 2;

    // Send messages concurrently
    cilk_spawn send_message("buffered");
    cilk_spawn send_message("channel");

    cilk_sync;

    // Receive and print messages
    for (int i = 0; i < buffer_size; ++i) {
        std::string msg = receive_message();
        if (!msg.empty()) {
            std::cout << msg << std::endl;
        }
    }

    return 0;
}

In this Cilk example, we’re simulating a buffered channel using a std::deque and a mutex for thread-safe operations. The send_message function adds messages to the deque, while receive_message retrieves and removes messages from it.

We use cilk_spawn to send messages concurrently, simulating the behavior of sending to a buffered channel without a corresponding receiver. The cilk_sync ensures all spawned tasks are completed before we start receiving messages.

The main function simulates sending two messages to the “buffered channel” and then receiving and printing them.

To compile and run this Cilk program:

$ cilk++ -std=c++11 channel_buffering.cilk -o channel_buffering
$ ./channel_buffering
buffered
channel

This example demonstrates how we can achieve similar functionality to buffered channels in Cilk, even though the language doesn’t have built-in channel constructs. The use of Cilk’s parallel constructs allows for concurrent operations on our simulated channel.