What is a C++ Standard Library Clocks Library?
Table of Contents
Introduction
The C++ Standard Library’s Clocks Library, part of std::chrono, provides various types of clocks for measuring time intervals and capturing the current time. These clocks are designed to suit different needs, such as measuring wall-clock time, elapsed time, or high-resolution time. Understanding the different clocks available allows developers to select the most appropriate one for their specific requirements in C++.
Core Clocks in std::chrono
std::chrono::system_clock
1.1. Overview
The std::chrono::system_clock represents the wall-clock time and is used to obtain the current calendar time. It measures time based on the system’s real-time clock, making it suitable for operations involving calendar dates and times.
Example:
In this example, std::chrono::system_clock::now() retrieves the current time, and std::ctime() converts it to a human-readable format.
1.2. Applications
- Obtaining the current date and time.
- Time-stamping events or logs.
- Measuring elapsed time in real-world scenarios.
std::chrono::steady_clock
2.1. Overview
The std::chrono::steady_clock provides a monotonically increasing clock that is not affected by system clock changes. It is ideal for measuring intervals or durations because it guarantees that time will only advance and will not be adjusted.
Example:
This example uses std::chrono::steady_clock to measure the duration of a sleep operation.
2.2. Applications
- Measuring execution time of code blocks.
- Timing intervals for performance measurements.
- Scheduling tasks or delays where accuracy over time is critical.
std::chrono::high_resolution_clock
3.1. Overview
The std::chrono::high_resolution_clock is designed to provide the highest available resolution clock. It is often implemented as an alias for either system_clock or steady_clock, depending on the platform. This clock is used when very precise time measurements are needed.
Example:
This example measures the elapsed time with high precision using std::chrono::high_resolution_clock.
3.2. Applications
- Detailed performance profiling and benchmarking.
- Fine-grained time measurements for high-precision applications.
Practical Examples
Example 1: Benchmarking Code Performance
Use std::chrono::high_resolution_clock to measure and compare the performance of different code segments.
Example:
This example benchmarks two functions with different execution times.
Example 2: Scheduling Delays
Use std::chrono::steady_clock to create timed delays in programs.
Example:
This example demonstrates scheduling a delay and measuring its duration.
Conclusion
The C++ Standard Library Clocks Library, part of std::chrono, includes several clocks such as system_clock, steady_clock, and high_resolution_clock. These clocks offer various features for measuring real-time, elapsed time, and high-resolution time intervals. By choosing the appropriate clock, developers can accurately track time, measure performance, and manage delays in their C++ applications.