Re: Speed comparison of regex versus index, lc, and / /i

On Fri, 30 May 2008 13:28:21 +0000, John W. Krahn wrote:

Just the opposite. AFAIK if searching for a literal string (as opposed
to a regular expression pattern) the regexp engine will use the same
algorithm as index().

I don't know what it does internally, but actually using non-literal
strings in the regular expression match like "something|else" or
"first.*second" did not result in a significant slowdown. The search
string did not change at all during the execution of the program, so
the regular expression would only have been compiled once.

I assume that most of the slowdown was caused by the introduction of the
use of UTF, etc.

No - the "lc"-related slowdown was experienced even if I read in the
files as bytes and did not convert them into anything. I'm sure of
this because I converted to using UTF-8 halfway through coding because
of an unrelated problem, and by that point I'd already noticed that "lc"
or / /i more than doubled the time of the program execution. In fact at the
same time that I converted the searched files into UTF-8, I also converted
them to lower case.


.

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