Promise and Future: Return a Notification

Explore how promises and futures can be used to synchronize threads in C++ more simply and safely than condition variables. Understand their single-notification behavior, error handling, and avoidance of spurious wakeups. See examples of task-based thread communication using promise and future pairs for notification.

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If you use promises and futures to synchronize threads, they have a lot in common with condition variables. Most of the time, promises and futures are the better choices. Before I present you an example, here is the big picture.

Criteria	Condition Variables	Tasks

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1.Introduction

2.A Quick Overview

3.Memory Model: The Contract

4.Memory Model: Atomics

5.Memory Model: Synchronization and Ordering Constraints

6.Memory Model: Fences

7.Multithreading: Threads

8.Multithreading: Shared Data

9.Multithreading: Local Data

10.Multithreading: Condition Variables

11.Multithreading: Tasks

12.Case Study: Calculate Sum of a Vector

13.Case Study: Thread-Safe Initialization of a Singleton

14.Case Study: Ongoing Optimization with CppMem

15.Parallel Algorithms of the Standard Template Library

16.The Future: C++20

17.Coding Examples

18.Best Practices

19.The Time Library

20.Glossary

21.About the Author

Promise and Future: Return a Notification