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204 lines
6.2 KiB
204 lines
6.2 KiB
#!/usr/bin/env python |
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# Copyright 2005 Google Inc. All Rights Reserved. |
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# |
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# Licensed under the Apache License, Version 2.0 (the "License"); |
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# you may not use this file except in compliance with the License. |
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# You may obtain a copy of the License at |
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# |
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# http://www.apache.org/licenses/LICENSE-2.0 |
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# |
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# Unless required by applicable law or agreed to in writing, software |
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# distributed under the License is distributed on an "AS-IS" BASIS, |
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
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# See the License for the specific language governing permissions and |
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# limitations under the License. |
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"""A useful class for digesting, on a high-level, where time in a program goes. |
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Usage: |
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sw = StopWatch() |
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sw.start() |
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sw.start('foo') |
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foo() |
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sw.stop('foo') |
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args = overhead_code() |
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sw.start('bar') |
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bar(args) |
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sw.stop('bar') |
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sw.dump() |
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If you start a new timer when one is already running, then the other one will |
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stop running, and restart when you stop this timer. This behavior is very |
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useful for when you want to try timing for a subcall without remembering |
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what is already running. For instance: |
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sw.start('all_this') |
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do_some_stuff() |
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sw.start('just_that') |
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small_but_expensive_function() |
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sw.stop('just_that') |
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cleanup_code() |
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sw.stop('all_this') |
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In this case, the output will be what you want: the time spent in |
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small_but_expensive function will show up in the timer for just_that and not |
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all_this. |
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""" |
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import StringIO |
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import time |
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__owner__ = 'dbentley@google.com (Dan Bentley)' |
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class StopWatch(object): |
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"""Class encapsulating a timer; see above for example usage. |
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Instance variables: |
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timers: map of stopwatch name -> time for each currently running stopwatch, |
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where time is seconds from the epoch of when this stopwatch was |
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started. |
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accum: map of stopwatch name -> accumulated time, in seconds, it has |
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already been run for. |
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stopped: map of timer name -> list of timer names that are blocking it. |
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counters: map of timer name -> number of times it has been started. |
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""" |
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def __init__(self): |
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self.timers = {} |
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self.accum = {} |
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self.stopped = {} |
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self.counters = {} |
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def start(self, timer='total', stop_others=True): |
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"""Start a timer. |
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Args: |
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timer: str; name of the timer to start, defaults to the overall timer. |
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stop_others: bool; if True, stop all other running timers. If False, then |
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you can have time that is spent inside more than one timer |
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and there's a good chance that the overhead measured will be |
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negative. |
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""" |
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if stop_others: |
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stopped = [] |
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for other in list(self.timers): |
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if not other == 'total': |
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self.stop(other) |
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stopped.append(other) |
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self.stopped[timer] = stopped |
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self.counters[timer] = self.counters.get(timer, 0) + 1 |
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self.timers[timer] = time.time() |
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def stop(self, timer='total'): |
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"""Stop a running timer. |
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This includes restarting anything that was stopped on behalf of this timer. |
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Args: |
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timer: str; name of the timer to stop, defaults to the overall timer. |
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Raises: |
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RuntimeError: if timer refers to a timer that was never started. |
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""" |
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if timer not in self.timers: |
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raise RuntimeError( |
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'Tried to stop timer that was never started: %s' % timer) |
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self.accum[timer] = self.timervalue(timer) |
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del self.timers[timer] |
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for stopped in self.stopped.get(timer, []): |
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self.start(stopped, stop_others=0) |
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def timervalue(self, timer='total', now=None): |
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"""Return the value seen by this timer so far. |
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If the timer is stopped, this will be the accumulated time it has seen. |
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If the timer is running, this will be the time it has seen up to now. |
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If the timer has never been started, this will be zero. |
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Args: |
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timer: str; the name of the timer to report on. |
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now: long; if provided, the time to use for 'now' for running timers. |
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""" |
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if not now: |
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now = time.time() |
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if timer in self.timers: |
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# Timer is running now. |
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return self.accum.get(timer, 0.0) + (now - self.timers[timer]) |
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elif timer in self.accum: |
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# Timer is stopped. |
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return self.accum[timer] |
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else: |
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# Timer is never started. |
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return 0.0 |
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def overhead(self, now=None): |
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"""Calculate the overhead. |
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Args: |
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now: (optional) time to use as the current time. |
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Returns: |
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The overhead, that is, time spent in total but not in any sub timer. This |
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may be negative if time was counted in two sub timers. Avoid this by |
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always using stop_others. |
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""" |
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total = self.timervalue('total', now) |
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if total == 0.0: |
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return 0.0 |
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all_timers = sum(self.accum.itervalues()) |
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return total - (all_timers - total) |
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def results(self, verbose=False): |
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"""Get the results of this stopwatch. |
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Args: |
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verbose: bool; if True, show all times; otherwise, show only the total. |
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Returns: |
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A list of tuples showing the output of this stopwatch, of the form |
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(name, value, num_starts) for each timer. Note that if the total timer |
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is not used, non-verbose results will be the empty list. |
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""" |
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now = time.time() |
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all_names = self.accum.keys() |
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names = [] |
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if 'total' in all_names: |
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all_names.remove('total') |
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all_names.sort() |
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if verbose: |
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names = all_names |
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results = [(name, self.timervalue(name, now=now), self.counters[name]) |
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for name in names] |
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if verbose: |
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results.append(('overhead', self.overhead(now=now), 1)) |
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if 'total' in self.accum or 'total' in self.timers: |
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results.append(('total', self.timervalue('total', now=now), |
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self.counters['total'])) |
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return results |
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def dump(self, verbose=False): |
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"""Describes where time in this stopwatch was spent. |
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Args: |
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verbose: bool; if True, show all timers; otherwise, show only the total. |
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Returns: |
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A string describing the stopwatch. |
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""" |
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output = StringIO.StringIO() |
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results = self.results(verbose=verbose) |
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maxlength = max([len(result[0]) for result in results]) |
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for result in results: |
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output.write('%*s: %6.2fs\n' % (maxlength, result[0], result[1])) |
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return output.getvalue() |
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# Create a stopwatch to be publicly used. |
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sw = StopWatch()
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