Is `DateTime.Now` the Best Way to Benchmark Function Performance?

Benchmarking Function Performance with DateTime.Now: Best Practices

Accurate measurement of function performance is critical for performance optimization. But is using DateTime.Now the ideal approach?

Question: Does the following code effectively use DateTime.Now to measure performance?

DateTime startTime = DateTime.Now;

// 执行过程

DateTime endTime = DateTime.Now;
TimeSpan totalTimeTaken = endTime.Subtract(startTime);

Answer: No, there are more suitable options.

Recommended method: Use the System.Diagnostics class in the Stopwatch namespace.

Stopwatch sw = Stopwatch.StartNew();
PerformWork();
sw.Stop();

Console.WriteLine("Time taken: {0}ms", sw.Elapsed.TotalMilliseconds);

Why is Stopwatch recommended:

• High Accuracy: StopwatchUtilize high-precision timers when available.
• Auto-detection: It checks for high frequency counters on the hardware.
• Resolution improvements: DateTime.UtcNow typically provides 15ms resolution, while Stopwatch aims for higher accuracy.

Other notes:

• Due to time zones and daylight saving time processing, DateTime.Now may be slower than DateTime.UtcNow.
• If high-precision hardware counters are not available, Stopwatch will fall back to DateTime.UtcNow.
• To determine whether Stopwatch uses a hardware counter, check the Stopwatch.IsHighResolution attribute.

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