C++ Multi-Threading Technologies: Complete Guide and Index

This guide provides an overview of essential C++ multi-threading technologies with links to detailed implementations and examples.

Table of Contents

  1. Overview
  2. Synchronization Primitives
  3. Thread Management
  4. Async Operations
  5. Atomic Operations
  6. Coordination Primitives
  7. Choosing the Right Technology

Overview

C++ provides a comprehensive set of multi-threading technologies for building concurrent applications. Each technology serves specific purposes and has different performance characteristics.

Technology Categories

  • Synchronization: Mutex, locks, condition variables
  • Thread Management: Thread creation, joining, detaching
  • Async Operations: Futures, promises, async
  • Atomic Operations: Lock-free programming
  • Coordination: Barriers, latches, semaphores

Synchronization Primitives

1. Mutex

Purpose: Provide exclusive access to shared resources.

Use Cases:

  • Protecting shared data
  • Critical sections
  • Thread-safe data structures

Links:

Key Concepts:

  • std::mutex
  • std::recursive_mutex
  • std::timed_mutex
  • std::shared_mutex (C++17)
  • lock_guard, unique_lock, scoped_lock

2. Condition Variable

Purpose: Enable threads to wait for specific conditions.

Use Cases:

  • Producer-consumer queues
  • Thread coordination
  • Event waiting

Links:

Key Concepts:

  • std::condition_variable
  • wait(), wait_for(), wait_until()
  • notify_one(), notify_all()
  • Predicate-based waiting

3. Semaphore (C++20)

Purpose: Control access to a resource with a counter.

Use Cases:

  • Resource limiting
  • Rate limiting
  • Bounded concurrency

Key Concepts:

  • std::counting_semaphore
  • std::binary_semaphore
  • acquire(), release()

Thread Management

4. std::thread

Purpose: Create and manage threads.

Use Cases:

  • Parallel execution
  • Background tasks
  • Worker threads

Key Concepts:

  • Thread creation
  • join(), detach()
  • Thread IDs
  • Hardware concurrency

5. Thread Local Storage

Purpose: Per-thread variables.

Use Cases:

  • Thread-specific data
  • Per-thread caches
  • Thread context

Key Concepts:

  • thread_local keyword
  • Thread-local storage duration

Async Operations

6. std::future and std::promise

Purpose: Get results from async operations.

Use Cases:

  • Async task results
  • One-time event communication
  • Thread communication

Key Concepts:

  • std::future
  • std::promise
  • get(), wait(), wait_for()
  • std::shared_future

7. std::async

Purpose: Execute functions asynchronously.

Use Cases:

  • Parallel function execution
  • Async I/O
  • Background computation

Key Concepts:

  • std::async()
  • Launch policies
  • Future-based results

Atomic Operations

8. std::atomic

Purpose: Lock-free atomic operations.

Use Cases:

  • Counters
  • Flags
  • Lock-free data structures

Key Concepts:

  • std::atomic<T>
  • load(), store(), exchange()
  • compare_exchange_weak/strong()
  • Memory ordering

9. Atomic Operations and Memory Ordering

Purpose: Fine-grained control over memory synchronization.

Use Cases:

  • Lock-free programming
  • Performance-critical sections
  • Custom synchronization

Key Concepts:

  • Memory orderings: relaxed, acquire, release, acq_rel, seq_cst
  • Fences
  • Atomic operations

Coordination Primitives

10. std::barrier (C++20)

Purpose: Synchronize multiple threads at a point.

Use Cases:

  • Multi-phase algorithms
  • Parallel computation
  • Synchronized processing

Links:

Key Concepts:

  • std::barrier
  • Phase synchronization
  • Completion functions

11. std::latch (C++20)

Purpose: One-time countdown synchronization.

Use Cases:

  • Thread initialization
  • One-time coordination
  • Countdown scenarios

Links:

Key Concepts:

  • std::latch
  • Countdown mechanism
  • One-time use

Choosing the Right Technology

Decision Matrix

Scenario Recommended Technology
Protect shared data std::mutex
Wait for condition std::condition_variable
Lock-free counter std::atomic
Async result std::future / std::promise
Parallel execution std::thread / std::async
Multi-phase sync std::barrier
One-time sync std::latch
Resource limiting std::counting_semaphore

Selection Guidelines

  1. Performance: Atomic operations for simple cases, mutex for complex
  2. Complexity: Start with mutex, use atomics only when needed
  3. Blocking: Use condition variables for waiting, futures for results
  4. Coordination: Use barriers/latches for synchronization points
  5. C++ Standard: Check C++ version for available features

Summary

C++ provides comprehensive multi-threading technologies:

  • Synchronization: Mutex, condition variables, semaphores
  • Thread Management: Thread creation and management
  • Async Operations: Futures, promises, async
  • Atomic Operations: Lock-free programming
  • Coordination: Barriers, latches

Key Takeaways

  • Choose technology based on specific needs
  • Understand performance characteristics
  • Use RAII wrappers for safety
  • Consider C++ standard version
  • Profile before optimizing

By understanding these technologies, you can build efficient, safe concurrent applications in C++.