| #!/usr/bin/env python |
| |
| # Copyright 2011 Google Inc. All Rights Reserved. |
| # |
| # Licensed under the Apache License, Version 2.0 (the "License"); |
| # you may not use this file except in compliance with the License. |
| # You may obtain a copy of the License at |
| # |
| # http://www.apache.org/licenses/LICENSE-2.0 |
| # |
| # Unless required by applicable law or agreed to in writing, software |
| # distributed under the License is distributed on an "AS IS" BASIS, |
| # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| # See the License for the specific language governing permissions and |
| # limitations under the License. |
| |
| """measure the runtime of a command by repeatedly running it. |
| """ |
| |
| import time |
| import subprocess |
| import sys |
| |
| devnull = open('/dev/null', 'w') |
| |
| def run(cmd, repeat=10): |
| print 'sampling:', |
| sys.stdout.flush() |
| |
| samples = [] |
| for _ in range(repeat): |
| start = time.time() |
| subprocess.call(cmd, stdout=devnull, stderr=devnull) |
| end = time.time() |
| dt = (end - start) * 1000 |
| print '%dms' % int(dt), |
| sys.stdout.flush() |
| samples.append(dt) |
| print |
| |
| # We're interested in the 'pure' runtime of the code, which is |
| # conceptually the smallest time we'd see if we ran it enough times |
| # such that it got the perfect time slices / disk cache hits. |
| best = min(samples) |
| # Also print how varied the outputs were in an attempt to make it |
| # more obvious if something has gone terribly wrong. |
| err = sum(s - best for s in samples) / float(len(samples)) |
| print 'estimate: %dms (mean err %.1fms)' % (best, err) |
| |
| if __name__ == '__main__': |
| if len(sys.argv) < 2: |
| print 'usage: measure.py command args...' |
| sys.exit(1) |
| run(cmd=sys.argv[1:]) |