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pdr@google.com authored
https://bugs.webkit.org/show_bug.cgi?id=98115 Reviewed by Ryosuke Niwa. Previously our standard deviation calculation was incorrect. This patch updates perftest.py's algorithm to calculate the sample standard deviation (with Bessel's correction) using Knuth's online algorithm: http://en.wikipedia.org/wiki/Algorithms_for_calculating_variance#Online_algorithm An existing test has been modified to prove our new results. This patch also updates runner.js to use Bessel's correction in its sample standard deviation calculation, which is more accurate for small sample sizes. Additionally, runner.js has been modified to not calculate the 'sum' statistic, which was not very useful. PerformanceTests: * resources/runner.js: (PerfTestRunner.computeStatistics): Tools: * Scripts/webkitpy/performance_tests/perftest.py: The unused variable valueSum has also been removed. (PageLoadingPerfTest.run): * Scripts/webkitpy/performance_tests/perftest_unittest.py: This test calculates the stdev of {2000, 3000, ..., 20000} which was hand-calculated using a spreadsheet. (TestPageLoadingPerfTest.test_run): LayoutTests: * fast/harness/perftests/perf-runner-compute-statistics-expected.txt: * fast/harness/perftests/perf-runner-compute-statistics.html: * fast/harness/perftests/runs-per-second-log-expected.txt: git-svn-id: http://svn.webkit.org/repository/webkit/trunk@130135 268f45cc-cd09-0410-ab3c-d52691b4dbfc
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