375 lines
13 KiB
Python
375 lines
13 KiB
Python
#! /usr/bin/env python3
|
|
|
|
"""Tool for measuring execution time of small code snippets.
|
|
|
|
This module avoids a number of common traps for measuring execution
|
|
times. See also Tim Peters' introduction to the Algorithms chapter in
|
|
the Python Cookbook, published by O'Reilly.
|
|
|
|
Library usage: see the Timer class.
|
|
|
|
Command line usage:
|
|
python timeit.py [-n N] [-r N] [-s S] [-p] [-h] [--] [statement]
|
|
|
|
Options:
|
|
-n/--number N: how many times to execute 'statement' (default: see below)
|
|
-r/--repeat N: how many times to repeat the timer (default 3)
|
|
-s/--setup S: statement to be executed once initially (default 'pass').
|
|
Execution time of this setup statement is NOT timed.
|
|
-p/--process: use time.process_time() (default is time.perf_counter())
|
|
-v/--verbose: print raw timing results; repeat for more digits precision
|
|
-u/--unit: set the output time unit (nsec, usec, msec, or sec)
|
|
-h/--help: print this usage message and exit
|
|
--: separate options from statement, use when statement starts with -
|
|
statement: statement to be timed (default 'pass')
|
|
|
|
A multi-line statement may be given by specifying each line as a
|
|
separate argument; indented lines are possible by enclosing an
|
|
argument in quotes and using leading spaces. Multiple -s options are
|
|
treated similarly.
|
|
|
|
If -n is not given, a suitable number of loops is calculated by trying
|
|
successive powers of 10 until the total time is at least 0.2 seconds.
|
|
|
|
Note: there is a certain baseline overhead associated with executing a
|
|
pass statement. It differs between versions. The code here doesn't try
|
|
to hide it, but you should be aware of it. The baseline overhead can be
|
|
measured by invoking the program without arguments.
|
|
|
|
Classes:
|
|
|
|
Timer
|
|
|
|
Functions:
|
|
|
|
timeit(string, string) -> float
|
|
repeat(string, string) -> list
|
|
default_timer() -> float
|
|
|
|
"""
|
|
|
|
import gc
|
|
import sys
|
|
import time
|
|
import itertools
|
|
|
|
__all__ = ["Timer", "timeit", "repeat", "default_timer"]
|
|
|
|
dummy_src_name = "<timeit-src>"
|
|
default_number = 1000000
|
|
default_repeat = 5
|
|
default_timer = time.perf_counter
|
|
|
|
_globals = globals
|
|
|
|
# Don't change the indentation of the template; the reindent() calls
|
|
# in Timer.__init__() depend on setup being indented 4 spaces and stmt
|
|
# being indented 8 spaces.
|
|
template = """
|
|
def inner(_it, _timer{init}):
|
|
{setup}
|
|
_t0 = _timer()
|
|
for _i in _it:
|
|
{stmt}
|
|
_t1 = _timer()
|
|
return _t1 - _t0
|
|
"""
|
|
|
|
def reindent(src, indent):
|
|
"""Helper to reindent a multi-line statement."""
|
|
return src.replace("\n", "\n" + " "*indent)
|
|
|
|
class Timer:
|
|
"""Class for timing execution speed of small code snippets.
|
|
|
|
The constructor takes a statement to be timed, an additional
|
|
statement used for setup, and a timer function. Both statements
|
|
default to 'pass'; the timer function is platform-dependent (see
|
|
module doc string). If 'globals' is specified, the code will be
|
|
executed within that namespace (as opposed to inside timeit's
|
|
namespace).
|
|
|
|
To measure the execution time of the first statement, use the
|
|
timeit() method. The repeat() method is a convenience to call
|
|
timeit() multiple times and return a list of results.
|
|
|
|
The statements may contain newlines, as long as they don't contain
|
|
multi-line string literals.
|
|
"""
|
|
|
|
def __init__(self, stmt="pass", setup="pass", timer=default_timer,
|
|
globals=None):
|
|
"""Constructor. See class doc string."""
|
|
self.timer = timer
|
|
local_ns = {}
|
|
global_ns = _globals() if globals is None else globals
|
|
init = ''
|
|
if isinstance(setup, str):
|
|
# Check that the code can be compiled outside a function
|
|
compile(setup, dummy_src_name, "exec")
|
|
stmtprefix = setup + '\n'
|
|
setup = reindent(setup, 4)
|
|
elif callable(setup):
|
|
local_ns['_setup'] = setup
|
|
init += ', _setup=_setup'
|
|
stmtprefix = ''
|
|
setup = '_setup()'
|
|
else:
|
|
raise ValueError("setup is neither a string nor callable")
|
|
if isinstance(stmt, str):
|
|
# Check that the code can be compiled outside a function
|
|
compile(stmtprefix + stmt, dummy_src_name, "exec")
|
|
stmt = reindent(stmt, 8)
|
|
elif callable(stmt):
|
|
local_ns['_stmt'] = stmt
|
|
init += ', _stmt=_stmt'
|
|
stmt = '_stmt()'
|
|
else:
|
|
raise ValueError("stmt is neither a string nor callable")
|
|
src = template.format(stmt=stmt, setup=setup, init=init)
|
|
self.src = src # Save for traceback display
|
|
code = compile(src, dummy_src_name, "exec")
|
|
exec(code, global_ns, local_ns)
|
|
self.inner = local_ns["inner"]
|
|
|
|
def print_exc(self, file=None):
|
|
"""Helper to print a traceback from the timed code.
|
|
|
|
Typical use:
|
|
|
|
t = Timer(...) # outside the try/except
|
|
try:
|
|
t.timeit(...) # or t.repeat(...)
|
|
except:
|
|
t.print_exc()
|
|
|
|
The advantage over the standard traceback is that source lines
|
|
in the compiled template will be displayed.
|
|
|
|
The optional file argument directs where the traceback is
|
|
sent; it defaults to sys.stderr.
|
|
"""
|
|
import linecache, traceback
|
|
if self.src is not None:
|
|
linecache.cache[dummy_src_name] = (len(self.src),
|
|
None,
|
|
self.src.split("\n"),
|
|
dummy_src_name)
|
|
# else the source is already stored somewhere else
|
|
|
|
traceback.print_exc(file=file)
|
|
|
|
def timeit(self, number=default_number):
|
|
"""Time 'number' executions of the main statement.
|
|
|
|
To be precise, this executes the setup statement once, and
|
|
then returns the time it takes to execute the main statement
|
|
a number of times, as a float measured in seconds. The
|
|
argument is the number of times through the loop, defaulting
|
|
to one million. The main statement, the setup statement and
|
|
the timer function to be used are passed to the constructor.
|
|
"""
|
|
it = itertools.repeat(None, number)
|
|
gcold = gc.isenabled()
|
|
gc.disable()
|
|
try:
|
|
timing = self.inner(it, self.timer)
|
|
finally:
|
|
if gcold:
|
|
gc.enable()
|
|
return timing
|
|
|
|
def repeat(self, repeat=default_repeat, number=default_number):
|
|
"""Call timeit() a few times.
|
|
|
|
This is a convenience function that calls the timeit()
|
|
repeatedly, returning a list of results. The first argument
|
|
specifies how many times to call timeit(), defaulting to 3;
|
|
the second argument specifies the timer argument, defaulting
|
|
to one million.
|
|
|
|
Note: it's tempting to calculate mean and standard deviation
|
|
from the result vector and report these. However, this is not
|
|
very useful. In a typical case, the lowest value gives a
|
|
lower bound for how fast your machine can run the given code
|
|
snippet; higher values in the result vector are typically not
|
|
caused by variability in Python's speed, but by other
|
|
processes interfering with your timing accuracy. So the min()
|
|
of the result is probably the only number you should be
|
|
interested in. After that, you should look at the entire
|
|
vector and apply common sense rather than statistics.
|
|
"""
|
|
r = []
|
|
for i in range(repeat):
|
|
t = self.timeit(number)
|
|
r.append(t)
|
|
return r
|
|
|
|
def autorange(self, callback=None):
|
|
"""Return the number of loops so that total time >= 0.2.
|
|
|
|
Calls the timeit method with increasing numbers from the sequence
|
|
1, 2, 5, 10, 20, 50, ... until the time taken is at least 0.2
|
|
second. Returns (number, time_taken).
|
|
|
|
If *callback* is given and is not None, it will be called after
|
|
each trial with two arguments: ``callback(number, time_taken)``.
|
|
"""
|
|
i = 1
|
|
while True:
|
|
for j in 1, 2, 5:
|
|
number = i * j
|
|
time_taken = self.timeit(number)
|
|
if callback:
|
|
callback(number, time_taken)
|
|
if time_taken >= 0.2:
|
|
return (number, time_taken)
|
|
i *= 10
|
|
|
|
def timeit(stmt="pass", setup="pass", timer=default_timer,
|
|
number=default_number, globals=None):
|
|
"""Convenience function to create Timer object and call timeit method."""
|
|
return Timer(stmt, setup, timer, globals).timeit(number)
|
|
|
|
def repeat(stmt="pass", setup="pass", timer=default_timer,
|
|
repeat=default_repeat, number=default_number, globals=None):
|
|
"""Convenience function to create Timer object and call repeat method."""
|
|
return Timer(stmt, setup, timer, globals).repeat(repeat, number)
|
|
|
|
def main(args=None, *, _wrap_timer=None):
|
|
"""Main program, used when run as a script.
|
|
|
|
The optional 'args' argument specifies the command line to be parsed,
|
|
defaulting to sys.argv[1:].
|
|
|
|
The return value is an exit code to be passed to sys.exit(); it
|
|
may be None to indicate success.
|
|
|
|
When an exception happens during timing, a traceback is printed to
|
|
stderr and the return value is 1. Exceptions at other times
|
|
(including the template compilation) are not caught.
|
|
|
|
'_wrap_timer' is an internal interface used for unit testing. If it
|
|
is not None, it must be a callable that accepts a timer function
|
|
and returns another timer function (used for unit testing).
|
|
"""
|
|
if args is None:
|
|
args = sys.argv[1:]
|
|
import getopt
|
|
try:
|
|
opts, args = getopt.getopt(args, "n:u:s:r:tcpvh",
|
|
["number=", "setup=", "repeat=",
|
|
"time", "clock", "process",
|
|
"verbose", "unit=", "help"])
|
|
except getopt.error as err:
|
|
print(err)
|
|
print("use -h/--help for command line help")
|
|
return 2
|
|
|
|
timer = default_timer
|
|
stmt = "\n".join(args) or "pass"
|
|
number = 0 # auto-determine
|
|
setup = []
|
|
repeat = default_repeat
|
|
verbose = 0
|
|
time_unit = None
|
|
units = {"nsec": 1e-9, "usec": 1e-6, "msec": 1e-3, "sec": 1.0}
|
|
precision = 3
|
|
for o, a in opts:
|
|
if o in ("-n", "--number"):
|
|
number = int(a)
|
|
if o in ("-s", "--setup"):
|
|
setup.append(a)
|
|
if o in ("-u", "--unit"):
|
|
if a in units:
|
|
time_unit = a
|
|
else:
|
|
print("Unrecognized unit. Please select nsec, usec, msec, or sec.",
|
|
file=sys.stderr)
|
|
return 2
|
|
if o in ("-r", "--repeat"):
|
|
repeat = int(a)
|
|
if repeat <= 0:
|
|
repeat = 1
|
|
if o in ("-p", "--process"):
|
|
timer = time.process_time
|
|
if o in ("-v", "--verbose"):
|
|
if verbose:
|
|
precision += 1
|
|
verbose += 1
|
|
if o in ("-h", "--help"):
|
|
print(__doc__, end=' ')
|
|
return 0
|
|
setup = "\n".join(setup) or "pass"
|
|
|
|
# Include the current directory, so that local imports work (sys.path
|
|
# contains the directory of this script, rather than the current
|
|
# directory)
|
|
import os
|
|
sys.path.insert(0, os.curdir)
|
|
if _wrap_timer is not None:
|
|
timer = _wrap_timer(timer)
|
|
|
|
t = Timer(stmt, setup, timer)
|
|
if number == 0:
|
|
# determine number so that 0.2 <= total time < 2.0
|
|
callback = None
|
|
if verbose:
|
|
def callback(number, time_taken):
|
|
msg = "{num} loop{s} -> {secs:.{prec}g} secs"
|
|
plural = (number != 1)
|
|
print(msg.format(num=number, s='s' if plural else '',
|
|
secs=time_taken, prec=precision))
|
|
try:
|
|
number, _ = t.autorange(callback)
|
|
except:
|
|
t.print_exc()
|
|
return 1
|
|
|
|
if verbose:
|
|
print()
|
|
|
|
try:
|
|
raw_timings = t.repeat(repeat, number)
|
|
except:
|
|
t.print_exc()
|
|
return 1
|
|
|
|
def format_time(dt):
|
|
unit = time_unit
|
|
|
|
if unit is not None:
|
|
scale = units[unit]
|
|
else:
|
|
scales = [(scale, unit) for unit, scale in units.items()]
|
|
scales.sort(reverse=True)
|
|
for scale, unit in scales:
|
|
if dt >= scale:
|
|
break
|
|
|
|
return "%.*g %s" % (precision, dt / scale, unit)
|
|
|
|
if verbose:
|
|
print("raw times: %s" % ", ".join(map(format_time, raw_timings)))
|
|
print()
|
|
timings = [dt / number for dt in raw_timings]
|
|
|
|
best = min(timings)
|
|
print("%d loop%s, best of %d: %s per loop"
|
|
% (number, 's' if number != 1 else '',
|
|
repeat, format_time(best)))
|
|
|
|
best = min(timings)
|
|
worst = max(timings)
|
|
if worst >= best * 4:
|
|
import warnings
|
|
warnings.warn_explicit("The test results are likely unreliable. "
|
|
"The worst time (%s) was more than four times "
|
|
"slower than the best time (%s)."
|
|
% (format_time(worst), format_time(best)),
|
|
UserWarning, '', 0)
|
|
return None
|
|
|
|
if __name__ == "__main__":
|
|
sys.exit(main())
|