How Can I Achieve Nanosecond Precision Timing in C Across Different Operating Systems?

Timer Function in C for Nanosecond Precision

When timing the execution of an API function in C , the built-in clock() function initially calculates the time elapsed in seconds. To obtain more precise measurements in nanoseconds, we need to delve into platform-specific timekeeping mechanisms.

Linux and BSD

For Linux and BSD operating systems, clock_gettime() is the recommended method:

#include <sys/time.h>

int main() {
    timespec ts;
    // For Linux, use: clock_gettime(CLOCK_REALTIME, &ts);
    // For FreeBSD, use: clock_gettime(CLOCK_MONOTONIC, &ts);
}

Windows

Windows offers the QueryPerformanceCounter function:

#include <windows.h>

int main() {
    LARGE_INTEGER ts;
    QueryPerformanceCounter(&ts);
}

Precision and Accuracy Considerations

While QueryPerformanceCounter provides higher resolution, it has certain limitations:

• It may exhibit inconsistencies on certain chipsets, especially AMD processors.
• Synchronization across multiple processors can be challenging.

Windows 7 and later versions attempt to address these issues by detecting processors with invariant TSC (Time Stamp Counter) and employing external timers when necessary.

Additional Resources

For further insights and troubleshooting, refer to these additional articles:

• https://msdn.microsoft.com/en-us/library/windows/desktop/ee417693(v=vs.85).aspx
• https://stackoverflow.com/a/4588605/34329
• https://blogs.oracle.com/dholmes/entry/inside_the_hotspot_vm_clocks
• https://performancebydesign.blogspot.com/2012/03/high-resolution-clocks-and-timers-for.html
• QueryPerformanceCounter Status?

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