Benchmark types and attributes

Benchmark attributes can either be applied directly to the benchmark function:

def time_something():

time_something.timeout = 123

or appear as class attributes:

class SomeBenchmarks(object):
    timeout = 123

    def time_something(self):

Benchmark types

The following benchmark types are recognized:

  • def time_*(): measure time taken by the function. See Timing.
  • def mem_*(): measure memory size of the object returned. See Memory.
  • def peakmem_*(): measure peak memory size of the process when calling the function. See Peak Memory.
  • def track_*(): use the returned numerical value as the benchmark result See Tracking (Generic).

Benchmark attributes


The following attributes are applicable to all benchmark types:

  • timeout: The amount of time, in seconds, to give the benchmark to run before forcibly killing it. Defaults to 60 seconds.

  • benchmark_name: If given, used as benchmark function name instead of generated one <module>.<class>.<function>.

  • pretty_name: If given, used to display the benchmark name instead of the benchmark function name.

  • pretty_source: If given, used to display a custom version of the benchmark source.

  • version: Used to determine when to invalidate old benchmark results. Benchmark results produced with a different value of the version than the current value will be ignored. The value can be any Python string (or other object, str() will be taken).

    Default (if version=None or not given): hash of the source code of the benchmark function and setup and setup_cache methods. If the source code of any of these changes, old results become invalidated.

  • setup: function to be called as a setup function for the benchmark See Setup and teardown functions for discussion.

  • teardown: function to be called as a teardown function for the benchmark See Setup and teardown functions for discussion.

  • setup_cache: function to be called as a cache setup function. See Setup and teardown functions for discussion.

  • param_names: list of parameter names See Parameterized benchmarks for discussion.

  • params: list of lists of parameter values. If there is only a single parameter, may also be a list of parameter values. See Parameterized benchmarks for discussion.


    def setup_func(n, func):
        print(n, func)
    def teardown_func(n, func):
        print(n, func)
    def time_ranges(n, func):
        for i in func(n):
    time_ranges.setup = setup_func
    time_ranges.param_names = ['n', 'func']
    time_ranges.params = ([10, 1000], [range, numpy.arange])

    The benchmark will be run for parameters (10, range), (10, numpy.arange), (1000, range), (1000, numpy.arange). The setup and teardown functions will also obtain these parameters.

    Note that setup_cache is not parameterized.

Timing benchmarks

  • warmup_time: asv will spend this time (in seconds) in calling the benchmarked function repeatedly, before starting to run the actual benchmark. If not specified, warmup_time defaults to 0.1 seconds (on PyPy, the default is 1.0 sec).

  • processes: How many processes to launch for running the benchmarks (default: 2). The processes run benchmarks in an interleaved order, allowing to sample over longer periods of background performance variations (e.g. CPU power levels).

  • repeat: The number measurement samples to collect per process. Each sample consists of running the benchmark number times. The median time from all samples is used as the final measurement result.

    repeat can be a tuple (min_repeat, max_repeat, max_time). In this case, the measurement first collects at least min_repeat samples, and continues until either max_repeat samples are collected or the collection time exceeds max_time.

    When not provided (repeat set to 0), the default value is (1, 10, 20.0) if processes==1 and (1, 5, 10.0) otherwise.

  • number: Manually choose the number of iterations in each sample. If number is specified, sample_time is ignored. Note that setup and teardown are not run between iterations: setup runs first, then the timed benchmark routine is called number times, and after that teardown runs.

  • sample_time: asv will automatically select number so that each sample takes approximatively sample_time seconds. If not specified, sample_time defaults to 10 milliseconds.

  • min_run_count: the function is run at least this many times during benchmark. Default: 2

  • timer: The timing function to use, which can be any source of monotonically increasing numbers, such as time.clock, time.time or time.process_time. If it’s not provided, it defaults to timeit.default_timer, but other useful values are process_time, for which asv provides a backported version for versions of Python prior to 3.3.

    Changed in version 0.4: Previously, the default timer measured process time, which was chosen to minimize noise from other processes. However, on Windows, this is only available at a resolution of 15.6ms, which is greater than the recommended benchmark runtime of 10ms. Therefore, we default to the highest resolution clock on any platform.

The sample_time, number, repeat, and timer attributes can be adjusted in the setup() routine, which can be useful for parameterized benchmarks.

Tracking benchmarks

  • unit: The unit of the values returned by the benchmark. Used for display in the web interface.

Environment variables

When asv runs benchmarks, several environment variables are defined, see ASV environment variables.