mpmc_queue_sample.cpp

Four examples: basic single-producer/single-consumer, multi-producer/ multi-consumer, batch enqueue/dequeue, and enqueue/dequeue performance measurement with statistics.

See also

lockfree_job_queue, callback_job

// BSD 3-Clause License
// Copyright (c) 2024, 🍀☀🌕🌥 🌊
// See the LICENSE file in the project root for full license information.
 
#include "thread_base/lockfree/queues/lockfree_job_queue.h"
#include "thread_base/jobs/callback_job.h"
#include "logger/core/logger.h"
 
#include <thread>
#include <vector>
#include <atomic>
#include <chrono>
#include <random>
 
using namespace kcenon::thread;
using namespace log_module;
using namespace std::chrono_literals;
 
// Example 1: Basic single producer, single consumer
void basic_spsc_example()
{
    write_information("[Example 1] Basic SPSC Pattern");
    
    lockfree_job_queue queue;
    std::atomic<int> counter{0};
    
    // Producer thread
    std::thread producer([&queue, &counter]() {
        for (int i = 0; i < 10; ++i) {
            auto job = std::make_unique<callback_job>([&counter, i]() -> kcenon::common::VoidResult {
                counter.fetch_add(1);
                write_information("Processed job {}", i);
                return kcenon::common::ok(); // Success
            });
            
            auto result = queue.enqueue(std::move(job));
            if (result.is_err()) {
                write_error(
                    "Failed to enqueue job {}: {}", i, result.error().message);
            }
            
            std::this_thread::sleep_for(10ms);
        }
        write_information("Producer finished");
    });
    
    // Consumer thread
    std::thread consumer([&queue, &counter]() {
        int consumed = 0;
        while (consumed < 10) {
            auto result = queue.dequeue();
            if (result.has_value()) {
                auto& job = result.value();
                auto work_result = job->do_work();
                if (work_result.is_ok()) {
                    // Job executed successfully
                    consumed++;
                } else {
                    write_error("Job failed: {}", work_result.error().message);
                }
            } else {
                std::this_thread::sleep_for(5ms);
            }
        }
        write_information("Consumer finished");
    });
    
    producer.join();
    consumer.join();
    
    write_information(
        "Total jobs processed: {}", counter.load());
}
 
// Example 2: Multiple producers, multiple consumers
void mpmc_example()
{
    write_information("\n[Example 2] MPMC Pattern");
    
    lockfree_job_queue queue;
    std::atomic<int> produced{0};
    std::atomic<int> consumed{0};
    const int num_producers = 3;
    const int num_consumers = 2;
    const int jobs_per_producer = 20;
    
    std::vector<std::thread> producers;
    std::vector<std::thread> consumers;
    
    // Start producers
    for (int p = 0; p < num_producers; ++p) {
        producers.emplace_back([&queue, &produced, p, jobs_per_producer]() {
            std::random_device rd;
            std::mt19937 gen(rd());
            std::uniform_int_distribution<> delay_dist(1, 10);
            
            for (int i = 0; i < jobs_per_producer; ++i) {
                auto job = std::make_unique<callback_job>(
                    [p, i]() -> kcenon::common::VoidResult {
                        write_information("Job from producer {} #{}", p, i);
                        return kcenon::common::ok();
                    });
                
                // Retry on failure (high contention scenario)
                while (true) {
                    auto result = queue.enqueue(std::move(job));
                    if (!result.is_err()) {
                        produced.fetch_add(1);
                        break;
                    }
                    std::this_thread::yield();
                }
                
                std::this_thread::sleep_for(std::chrono::milliseconds(delay_dist(gen)));
            }
            
            write_information(
                "Producer {} finished", p);
        });
    }
    
    // Start consumers
    for (int c = 0; c < num_consumers; ++c) {
        consumers.emplace_back([&queue, &consumed, c, num_producers, jobs_per_producer]() {
            const int total_jobs = num_producers * jobs_per_producer;
            
            while (consumed.load() < total_jobs) {
                auto result = queue.dequeue();
                if (result.has_value()) {
                    auto& job = result.value();
                    auto work_result = job->do_work();
                    if (work_result.is_ok()) {
                        // Job executed successfully
                        consumed.fetch_add(1);
                    } else {
                        write_error("Consumer {} job failed: {}", c, work_result.error().message);
                    }
                } else {
                    std::this_thread::sleep_for(1ms);
                }
            }
            
            write_information(
                "Consumer {} finished", c);
        });
    }
    
    // Wait for all threads
    for (auto& t : producers) t.join();
    for (auto& t : consumers) t.join();
    
    write_information(
        "Total produced: {}, consumed: {}", 
            produced.load(), consumed.load());
}
 
// Example 3: Batch operations
void batch_operations_example()
{
    write_information("\n[Example 3] Batch Operations");
    
    lockfree_job_queue queue;
    std::atomic<int> processed{0};
    
    // Batch enqueue
    std::vector<std::unique_ptr<job>> batch;
    for (int i = 0; i < 50; ++i) {
        batch.push_back(std::make_unique<callback_job>(
            [&processed, i]() -> kcenon::common::VoidResult {
                processed.fetch_add(1);
                write_information("Batch job {}", i);
                return kcenon::common::ok();
            }));
    }
    
    write_information(
        "Enqueueing {} jobs in batch", batch.size());
    
    auto enqueue_result = queue.enqueue_batch(std::move(batch));
    if (enqueue_result.is_err()) {
        write_error(
            "Batch enqueue failed: {}", enqueue_result.error().message);
        return;
    }
    
    // Batch dequeue
    auto dequeued = queue.dequeue_batch();
    write_information(
        "Dequeued {} jobs in batch", dequeued.size());
    
    // Process all dequeued jobs
    for (auto& job : dequeued) {
        auto result = job->do_work();
        if (result.is_ok()) {
            // Job executed successfully
        } else {
            write_error("Batch job failed: {}", result.error().message);
        }
    }
    
    write_information(
        "Total processed: {}", processed.load());
}
 
// Example 4: Performance measurement
void performance_example()
{
    write_information("\n[Example 4] Performance Measurement");
    
    lockfree_job_queue queue;
    const int num_operations = 100000;
    
    // Measure enqueue performance
    auto start = std::chrono::high_resolution_clock::now();
    
    for (int i = 0; i < num_operations; ++i) {
        auto job = std::make_unique<callback_job>([]() -> kcenon::common::VoidResult {
            return kcenon::common::ok();
        });
        
        while (true) {
            auto r = queue.enqueue(std::move(job));
            if (r.is_ok()) break;
            std::this_thread::yield();
            job = std::make_unique<callback_job>([]() -> kcenon::common::VoidResult { return kcenon::common::ok(); });
        }
    }
    
    auto enqueue_time = std::chrono::high_resolution_clock::now() - start;
    
    // Measure dequeue performance
    start = std::chrono::high_resolution_clock::now();
    
    for (int i = 0; i < num_operations; ++i) {
        while (true) {
            auto result = queue.dequeue();
            if (result.has_value()) {
                break;
            }
            std::this_thread::yield();
        }
    }
    
    auto dequeue_time = std::chrono::high_resolution_clock::now() - start;
    
    // Get statistics
    auto stats = queue.get_statistics();
    
    write_information(
        "Enqueue performance: {} ops in {} ms = {} ops/sec",
            num_operations,
            std::chrono::duration_cast<std::chrono::milliseconds>(enqueue_time).count(),
            num_operations * 1000.0 / std::chrono::duration_cast<std::chrono::milliseconds>(enqueue_time).count());
    
    write_information(
        "Dequeue performance: {} ops in {} ms = {} ops/sec",
            num_operations,
            std::chrono::duration_cast<std::chrono::milliseconds>(dequeue_time).count(),
            num_operations * 1000.0 / std::chrono::duration_cast<std::chrono::milliseconds>(dequeue_time).count());
    
    write_information(
        "Queue statistics:\n"
            "  Enqueued: {}\n"
            "  Dequeued: {}\n"
            "  Retries: {}\n"
            "  Average enqueue latency: {} ns\n"
            "  Average dequeue latency: {} ns",
            stats.enqueue_count,
            stats.dequeue_count,
            stats.retry_count,
            stats.get_average_enqueue_latency_ns(),
            stats.get_average_dequeue_latency_ns());
}
 
int main()
{
    log_module::start();
    log_module::console_target(log_types::Debug);
    
    write_information(
        "Lock-Free MPMC Queue Sample\n"
        "===========================");
    
    try {
        basic_spsc_example();
        mpmc_example();
        batch_operations_example();
        performance_example();
    } catch (const std::exception& e) {
        write_error(
            "Exception: {}", e.what());
    }
    
    write_information("\nAll examples completed!");
    
    log_module::stop();
    return 0;
}