27-Oct-2013 07:00, Andrei Alexandrescu пишет:
Hello,
A coworker implemented a system that spawns grep to rummage through a
large log file. Apparently doing so is quite a bit faster than using a
regex.
I would love to see how does the usage of regex looks like. Some numbers
would be just awesome. If regex is std.regex then also see:
https://github.com/D-Programming-Language/phobos/pull/1553
This is because grep is highly specialized and optimized. I was
wondering if we could implement a grepping library that builds on
regex's strengths and also grep's many optimization tricks:
If we talking D, then std.regex doesn't do Boyer-Moore search hence for
patterns that start with 100% fixed prefix it must be a great deal
slower. I'm using a ShiftOr search that has the benefit of being
applicable to fairly large class of prefixes (but it does look at every
byte).
There are also things a grep can do that in a general purpose library I
felt are just too heavy. A dedicated grep module could spent more time
on these tricks though knowing in advance that the input is going to be
quite large.
http://lists.freebsd.org/pipermail/freebsd-current/2010-August/019310.html
Andrei
--
Dmitry Olshansky
