C++ Multi-Threading Design Patterns: Complete Guide and Index

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

Table of Contents

  1. Overview
  2. Synchronization Patterns
  3. Execution Patterns
  4. Communication Patterns
  5. Coordination Patterns
  6. Advanced Patterns
  7. Choosing the Right Pattern

Overview

Multi-threading design patterns provide proven solutions to common concurrency problems. Each pattern addresses specific challenges in parallel programming.

Pattern Categories

  • Synchronization: Control access to shared resources
  • Execution: Manage task execution and thread lifecycle
  • Communication: Exchange data between threads
  • Coordination: Coordinate thread activities
  • Advanced: Complex patterns combining multiple concepts

Synchronization Patterns

1. Producer-Consumer Pattern

Purpose: Decouple data production from consumption using a shared buffer.

Use Cases:

  • Task queues
  • Event processing
  • Data pipelines
  • Logging systems

Links:

Key Concepts:

  • Thread-safe queue
  • Condition variables
  • Bounded buffers

2. Reader-Writer Pattern

Purpose: Allow multiple readers or exclusive writer access to shared data.

Use Cases:

  • Configuration management
  • Caches
  • Lookup tables
  • Read-heavy data structures

Links:

Key Concepts:

  • Shared mutex (C++17)
  • Read locks vs write locks
  • Reader-writer locks

3. Monitor Pattern

Purpose: Encapsulate shared data with synchronized access methods.

Use Cases:

  • Thread-safe data structures
  • Resource managers
  • State management

Key Concepts:

  • Mutex-protected methods
  • Condition variables
  • Encapsulation

Execution Patterns

4. Thread Pool Pattern

Purpose: Reuse threads to execute tasks from a queue.

Use Cases:

  • Web servers
  • Task processing
  • Parallel algorithms
  • Async operations

Links:

Key Concepts:

  • Worker threads
  • Task queue
  • Thread reuse

5. Active Object Pattern

Purpose: Encapsulate method calls as messages executed by a dedicated thread.

Use Cases:

  • GUI frameworks
  • Actor systems
  • Message-driven architectures

Key Concepts:

  • Method request queue
  • Scheduler thread
  • Future/promise for results

Communication Patterns

6. Message Passing Pattern

Purpose: Threads communicate by sending messages through queues.

Use Cases:

  • Actor systems
  • Microservices
  • Event-driven architectures

Key Concepts:

  • Message queues
  • Serialization
  • Asynchronous communication

7. Callback Pattern

Purpose: Execute callbacks asynchronously after task completion.

Use Cases:

  • Event handlers
  • Completion handlers
  • Progress reporting

Links:

Key Concepts:

  • Function pointers
  • std::function
  • Lambda expressions

Coordination Patterns

8. Barrier Pattern

Purpose: Synchronize multiple threads at specific points.

Use Cases:

  • Parallel algorithms
  • Multi-phase processing
  • Synchronized computation

Links:

Key Concepts:

  • std::barrier (C++20)
  • Phase synchronization
  • Reusable barriers

9. Latch Pattern

Purpose: One-time synchronization point for multiple threads.

Use Cases:

  • Initialization coordination
  • Thread startup
  • Countdown synchronization

Links:

Key Concepts:

  • std::latch (C++20)
  • Countdown mechanism
  • One-time use

Advanced Patterns

10. Gate + Thread Pool + Callback Queue

Purpose: Controlled async execution with result callbacks.

Use Cases:

  • Rate limiting
  • Resource management
  • State-dependent execution

Links:

Key Concepts:

  • Gate control
  • Thread pool execution
  • Callback queuing

11. Gated Callback Dispatcher

Purpose: Manage callback execution with gate-based control.

Use Cases:

  • Event systems
  • Notification systems
  • API callbacks

Links:

Key Concepts:

  • Callback queue
  • Gate control
  • Event-driven architecture

Choosing the Right Pattern

Decision Matrix

Scenario Recommended Pattern
Frequent reads, rare writes Reader-Writer
Data production/consumption Producer-Consumer
Reusable task execution Thread Pool
Multi-phase algorithms Barrier
One-time coordination Latch
Controlled async execution Gate + Thread Pool
Event handling Callback Dispatcher

Pattern Selection Guide

  1. Identify the problem: What are you trying to synchronize or coordinate?
  2. Analyze access patterns: Read-heavy, write-heavy, or balanced?
  3. Consider performance: Overhead vs. benefits
  4. Evaluate complexity: Simpler patterns first
  5. Test and measure: Profile to verify choice

Summary

Multi-threading design patterns provide structured solutions to concurrency challenges:

  • Synchronization patterns: Control shared resource access
  • Execution patterns: Manage thread and task lifecycle
  • Communication patterns: Enable thread communication
  • Coordination patterns: Synchronize thread activities
  • Advanced patterns: Combine multiple concepts

Key Takeaways

  • Choose patterns based on your specific needs
  • Start with simpler patterns
  • Profile performance before optimizing
  • Understand trade-offs between patterns
  • Combine patterns for complex scenarios

By understanding these patterns, you can build robust, efficient concurrent systems in C++.