Re: [exim] Hardware Sizing

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Autor: Philip Hazel
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A: Nigel Metheringham
CC: exim-users
Assumpte: Re: [exim] Hardware Sizing
On Thu, 8 Sep 2005, Nigel Metheringham wrote:

> However perl is normally pretty fast for regexp application (especially
> as you do need to do all that horrid UTF8 stuff) although there are
> cases that go really nasty.


Well, all I can say is that when I feed the PCRE pattern matching tests
to Perl, they run much more slowly. This is the main test, which has 704
different patterns, with various numbers of data lines:

Using pcretest:
real    0m0.003s
user    0m0.000s
sys     0m0.001s


Using Perl:
real    0m1.000s
user    0m0.974s
sys     0m0.007s


However, I haven't taken any measures to optimize the Perl (for example,
it probably recompiles each pattern for each match). Therefore, these
are "worst case" figures which no doubt could be improved. Nevertheless,
I would not expect Perl ever to be able to catch up: it is, after all,
essentially an interpreted language. You cannot expect it to be as fast
as compiled code. Even a few percent can be important when millions of
regex matches are happening.

-- 
Philip Hazel            University of Cambridge Computing Service,
ph10@???      Cambridge, England. Phone: +44 1223 334714.
Get the Exim 4 book:    http://www.uit.co.uk/exim-book