On 06/18/2013 09:51 PM, Steven D'Aprano wrote:
<SNIP>
Even if the regex engine is just as efficient at doing simple character
matching as `in`, and it probably isn't, your regex tries to match all
eleven characters of "ENQUEUEING" while the `in` test only has to match
three, "ENQ".
The rest of your post was valid, and useful, but there's a misconception
in this paragraph; I hope you don't mind me pointing it out.
In general, for simple substring searches, you can search for a large
string faster than you can search for a smaller one. I'd expect
if "ENQUEUING" in bigbuffer
to be faster than
if "ENQ" in bigbuffer
assuming that all occurrences of ENQ will actually match the whole
thing. If CPython's implementation doesn't show the speed difference,
maybe there's some room for optimization.
See Boyer-Moore if you want a peek at the algorithm.
When I was writiing a simple search program, I could typically search
for a 4-character string faster than REP SCASB could match a one
character string. And that's a single instruction (with prefix).
--
DaveA
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