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55 lines
1.7 KiB
Python
55 lines
1.7 KiB
Python
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#!/usr/bin/env python
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# Copyright 2011 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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"""measure the runtime of a command by repeatedly running it.
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"""
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import time
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import subprocess
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import sys
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devnull = open('/dev/null', 'w')
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def run(cmd, repeat=10):
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print 'sampling:',
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sys.stdout.flush()
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samples = []
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for _ in range(repeat):
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start = time.time()
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subprocess.call(cmd, stdout=devnull, stderr=devnull)
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end = time.time()
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dt = (end - start) * 1000
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print '%dms' % int(dt),
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sys.stdout.flush()
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samples.append(dt)
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print
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# We're interested in the 'pure' runtime of the code, which is
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# conceptually the smallest time we'd see if we ran it enough times
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# such that it got the perfect time slices / disk cache hits.
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best = min(samples)
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# Also print how varied the outputs were in an attempt to make it
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# more obvious if something has gone terribly wrong.
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err = sum(s - best for s in samples) / float(len(samples))
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print 'estimate: %dms (mean err %.1fms)' % (best, err)
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if __name__ == '__main__':
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if len(sys.argv) < 2:
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print 'usage: measure.py command args...'
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sys.exit(1)
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run(cmd=sys.argv[1:])
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