BSD-3-Clause licensed by Bryan O'Sullivan
Maintained by Marco Zocca <zocca.marco gmail>, Ryan Scott
This version can be pinned in stack with:criterion-measurement-,2107

Module documentation for

Used by 1 package in nightly-2021-07-23(full list with versions):


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Measurement-related functionality extracted from Criterion, with minimal dependencies. The rationale for this is to enable alternative analysis front-ends.


  • Change criterion_rdtsc to return mach_absolute_time on macOS. This is a portable way of returning the number of CPU cycles that works on both Intel- and ARM-based Macs.

  • Change criterion_gettime to use clock_gettime_nsec_np instead of mach_absolute_time on macOS. While mach_absolute_time has nanosecond resolution on Intel-based Macs, this is not the case on ARM-based Macs, so the previous mach_absolute_time-based implementation would return incorrect timing results on Apple silicon.

    There are two minor consequences of this change:

    • criterion-measurement now only supports macOS 10.02 or later, as that is the first version to have clock_gettime_nsec_np. As macOS 10.02 was released in 2002, this is unlikely to affect users, but please speak up if this is a problem for you.

    • As clock_gettime_nsec_np does not require any special initialization code, criterion_inittime is now a no-op on macOS. If you manually invoke the getTime function in your code, however, it is still important that you initializeTime beforehand, as this is still required for the Windows implementation to work correctly.

  • Ensure that Criterion.Measurement.Types.Internal is always compiled with optimizations, even if the criterion-measurement library itself happens to be built with -O0 or -fprof-auto. This is necessary to ensure that the inner benchmarking loop of criterion always finishes in a timely manner, even if the rest of the library is not fully optimized.

  • Add nfAppIO and whnfAppIO functions, which take a function and its argument separately like nf/whnf, but whose function returns IO like nfIO/whnfIO. This is useful for benchmarking functions in which the bulk of the work is not bound by IO, but by pure computations that might otherwise be optimized away if the argument is known statically.

  • This is the first release of criterion-measurement. The changelog notes below are copied from the notes for the corresponding criterion release, criterion-

  • Move the measurement functionality of criterion into a standalone package, criterion-measurement. In particular, cbits/ and Criterion.Measurement are now in criterion-measurement, along with the relevant definitions of Criterion.Types and Criterion.Types.Internal (both of which are now under the Criterion.Measurement.* namespace). Consequently, criterion now depends on criterion-measurement.

    This will let other libraries (e.g. alternative statistical analysis front-ends) to import the measurement functionality alone as a lightweight dependency.

  • Fix a bug on macOS and Windows where using runAndAnalyse and other lower-level benchmarking functions would result in an infinite loop.