Why Does std::chrono::high_resolution_clock Show Unexpected Deviations in Time Interval Measurements?

Resolution of std::chrono::high_resolution_clock in C

Problem:

When using std::chrono::high_resolution_clock to measure time intervals, the results consistently show deviations from the expected resolution. This deviation suggests that either the reported resolution is inaccurate or the measurement method is flawed.

Explanation:

The resolution of std::chrono::high_resolution_clock varies depending on the operating system and hardware configuration. However, it is generally assumed to be in the low nanosecond range. In the test program provided, the resolution is reported as 100 nanoseconds, but the measured time intervals are consistently in the range of 1-2 microseconds.

Troubleshooting and Solution:

To fix this discrepancy, it is important to consider the following factors:

1. Hardware limitations: The resolution of std::chrono::high_resolution_clock is ultimately limited by the hardware's capabilities. While the OS may provide a timer with microsecond precision, it is not guaranteed to have the necessary resolution for accurate measurements in the nanosecond range.
2. Measurement method: The test program measures the time taken by std::cout. However, this includes not only the execution time of the cout statement but also potential overhead from IO processing and system scheduling. This can introduce significant delays and contribute to the observed deviations.
3. Clock implementation: Visual Studio 2012 implements std::chrono::high_resolution_clock as a typedef for std::chrono::system_clock, which typically has millisecond resolution. This could explain the consistent deviations from expected high-resolution measurements.

Alternative Implementation:

If the standard high-resolution_clock implementation is not suitable for the required precision, an alternative implementation can be used. One option is the HighResClock library, which uses QueryPerformanceCounter to provide a timer with nanosecond resolution on Windows platforms.

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