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From: phillip@mirriwinni.cse.rmit.edu.au (Phillip Musumeci)
Newsgroups: comp.unix.bsd.freebsd.misc
Subject: Re: FreeBSD slower than Linux ?
Date: 31 Jan 1997 13:14:47 +1100
Organization: Computer Systems Engineering Department, RMIT Australia
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References: <dkleinh.854654600@isotope.ps.uci.edu>
<5crh6q$44j@synge.maths.tcd.ie>
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In-reply-to: dwmalone@maths.tcd.ie's message of 31 Jan 1997 01:17:14 -0000
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Xref: euryale.cc.adfa.oz.au comp.unix.bsd.freebsd.misc:34775
>>>>> "David" == David Malone <dwmalone@maths.tcd.ie> writes:
David> dkleinh@isotope.ps.uci.edu (Dirk Kleinhesselink) writes:
>> I'm compiling my program with the stock g77 that comes with each OS.
>> I know Linux is using gcc-2.7.2 and FreeBSD is using gcc-2.6.3 and
>> so I went back to my old Slackware 2.3, which has gcc-2.6.3 and this
>> was still twice as fast. Anyone have any ideas why ?
David> One thing that it might be is that the FreeBSD maths libraries
David> don't have FPU code in them the way they are distributed, if you
David> recompile them with HAVE_FPU=yes in /etc/make.conf this might
David> make quite a difference for some things.
Even though this could hurt people without FPUs, maybe we really should
have the standard system optimised for those with FPUs.
Note that the gcc compiler still includes compile time minimisation as one
of its goals when "-O" is used. If a job requires *very* long execution
times, then you should use "-O2" or even "-O4".
There may be further performance options that are relevant --- have a read
of the on-line info for gcc:
menu item * Invoking GCC::
submenu item * Optimize Options::
note the "-f" switches
(those such as "-ffast-math" should be read BEFORE possible use).
phillip
--
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UNIX _IS_ user friendly. It's just selective about who its friends are.
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