Re: How to make your Perl 30% faster

Using this probably depends on how much risk you can live with. Personally, I've always hesitated turning on extra optimization during compiles. For example, on AIX there is a caveat in the man pages for the built-in compiler of "The -O3 specific optimizations have the potential to alter the semantics of a user's program", which doesn't give me any warm feelings.

I'm not saying gcc is subject to this since I haven't used it in a while, but the fact that they don't enable these cool features by default seems to indicate they understand there is some risk involved.

Comment on Re: How to make your Perl 30% faster

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Re^2: How to make your Perl 30% faster by hardburn (Abbot) on Nov 16, 2004 at 17:28 UTC
Many of the optimizations make it hard to debug the program. Most of us don't debug the perl binary, so that's a non-issue. There are cases where optimization can break code. This is one good reason to have a good test suite. Usually it happens around particularly hairy code (IIRC, Duff's Device tends to trip up optimizers). Also, higher optimization levels may start trading off time for space, which might make someone still running Perl on an old VAX angry. In the general case of a regular Perl programmer, running on a reasonably up-to-date machine, higher optimization is fine. "There is no shame in being self-taught, only in not trying to learn in the first place." -- Atrus, Myst: The Book of D'ni.	[reply]
Re^3: How to make your Perl 30% faster by bluto (Curate) on Nov 16, 2004 at 18:43 UTC
Usually it happens around particularly hairy code. Kind of like the C code that perl itself is written in? :-)	[reply]
Re^3: How to make your Perl 30% faster by PetaMem (Priest) on Nov 17, 2004 at 07:54 UTC
Also, higher optimization levels may start trading off time for space, which might make someone still running Perl on an old VAX angry. Who is interested in an old VAX? ;-) But now that you mention it: -rwxr-xr-x 2 root root 11588 2004-11-17 09:49 /opt/perl-5.8.0_t/bin/perl -rwxr-xr-x 2 root root 1213952 2004-11-17 09:49 /usr/local/bin/perl Which looks really weird for me in the first case. Bye PetaMem All Perl: MT, NLP, NLU	[reply]
Re^4: How to make your Perl 30% faster by Joost (Canon) on Dec 10, 2004 at 21:04 UTC
/opt/perl-5.8.0_t/bin/perl is probably compiled with a shared perl library, while /usr/local/bin/perl is compiled statically. Look for libperl.so.* somewhere in your library path. :-) "What should it profit a man, if he should win a flame war, yet lose his cool?"	[reply]
Re^2: How to make your Perl 30% faster by PetaMem (Priest) on Nov 17, 2004 at 08:10 UTC
The original interpreter the "autovectorized" one was compared against was also compiled with -O3 as one can see in the updated node. All runs stable - at least on the P4 - don't know about other architectures, but sse2 is not of much interest there - I guess. Probably Mac/PPC users could experience similar results if GCC supports the altivec engine. Bye PetaMem All Perl: MT, NLP, NLU	[reply]