On 07/22/2010 01:34 PM, Georg Brandl wrote:
Timings (seconds to run the test suite):

re     26.689  26.015  26.008
regex  26.066  25.797  25.865

So, I thought there wasn't a difference in performance for this use case
(which is compiling a lot of regexes and matching most of them only a
few times in comparison).  However, I found that looking at the regex
caching is very important in this case: re._MAXCACHE is by default set to
100, and regex._MAXCACHE to 1024.  When I set re._MAXCACHE to 1024 before
running the test suite, I get times around 18 (!) seconds for re.

This seems to point to re being significantly *faster* than regexp, even in matching, and as such may be something the author would want to look into.

Nick writes:

> That still fits with the compile/match performance trade-off changes
> between re and regex though.

The performance trade-off should make regex slower with sufficiently small compiled regex cache, when a lot of time is wasted on compilation. But as the cache gets larger (and, for fairness, of the same size in both implementations), regex should outperform re. Georg, would you care to measure if there is a difference in performance with an even larger cache?
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