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Subject: Re: Intel C/C++ 5 for Linux free for noncommercial use

Author: Dann Corbit

Date: 12:24:00 11/12/01

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On November 12, 2001 at 15:18:00, Frank Phillips wrote:

>On November 11, 2001 at 18:53:00, Steve Timson wrote:
>
>>The installation was easy enough in Mandrake 8.1.  The only trick was (as others
>>have reported) that the shell script that sets up environment variables didn't
>>work, and I had to add the variables by hand to my .bashrc.  Also, the install
>>script first reported that it didn't recognize my hardware.  This is because
>>mandrake sets HOSTTYPE to i586 and the script was expecting i386.  A quick edit
>>of the install script to expect i586 fixed that.
>>
>>With a straight compile (just -O3) chester was about 2% faster than the gcc
>>version.  When I turned on -ipo which allows cross file optimizations, it got to
>>be about 10% faster than the gcc version.  This is on an athlon, no doubt
>>intel's own chips will probably see more benefit - but hey, I'll take the 10%..
>>:)
>>
>> - Steve
>>
>>
>Steve
>
>Try profiling you may be pleasantly surprised.  I got 30 percent in total over
>gcc.
>
>Some versions of -ipo would not compile with my Mandrake 8.1 and Tbird...

I try lots of different combinations.  When you use prof_genx, if you let it run
overnight (you better have a LOT of memory to do that) you will find a big
benefit when you use prof_use.

The version 6 beta has a bunch more helpful flags.  Some programs benefit a lot
from QaxM.

Sometimes it seems like something won't compile, but it just takes a really long
time.  That is especially true of LINT grammer outputs.  Compiling one module
from PostgreSQL takes nearly half an hour under full optimization.

Also, I think that the compiler will act flaky if you don't have enough memory
(in other words, I suspect that they don't always check the return of malloc()).

So to compile a large program you should have 500 megs of ram.

The code coach is sometimes useful (and sometimes just plain wrong).



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