On Fri, Oct 19, 2012 at 8:36 AM, Victor Stinner <victor.stin...@gmail.com>wrote:
> 2012/10/19 Benjamin Peterson <benja...@python.org>: > > It would be interesting to see how common it is for strings which have > > their hash computed to be compared. > > I implemented a quick hack. When running "./python -m test test_os": > Python calls PyUnicode_RichCompare() 15206 times with Py_EQ or Py_NE > operator. In 41.4% (6295 calls), the hash of the two operands is > known. In 41.2% (6262 times on 15206), the hash of the two operands > are known *and are different*! > > The hit rate may depend since when the process was started. For > example, in a fresh interpreter: the hit rate is only 7% (189 hit / > 2703 calls). > > When running the test suite, the hit rate is around 80% (hashs are > known in 90%) after running 70 tests. At the same time, the average of > string length is 4.1 characters and quite all strings are pure ASCII. > > I create the issue http://bugs.python.org/issue16286 to discuss this > optimization. > If you want to measure the performance impact compared to a clean build then you can use the unladen benchmarks as it contains several Python 3-compatible benchmarks now.
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