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Message-ID: <42545.108.15.196.189.1346255714.squirrel@webmail.tuffmail.net>
Date: Wed, 29 Aug 2012 11:55:14 -0400 (EDT)
From: "Brad Tilley" <brad@...ystems.com>
To: john-users@...ts.openwall.com
Subject: Re: Questions about compiling for Optimal CPU
Performance
Hi Magnum,
>> My older Intel Celeron CPU lists sse, sse2 and sse3 as supported in
>> /proc/cpuinfo, should I make-x86-sse2 or make-x86-native when compiling
>> jumbo-6? Or does the difference really matter?
>
> You should probably use linux-x86-64i. If you run a 32-bit OS, you should
> really ask yourself why.
You're joking, aren't you? Some CPUs are still 32-bit only or have 64-bit
capability, but disable it (such as some Intel Atoms). So when asked why,
that is the reason I sometimes use a 32-bit operating system and cannot
use a 64-bit OS for those specific CPUs. You can understand that I hope.
Not sure why this would be questioned... am I missing something? An inside
joke only related to JtR perhaps?
>> Also, the Makefile has two
>> possibilities for OpenMP...
>>
>> 1. -fopenmp
>> 2. -fopenmp -msse2
>>
>> Which one should be uncommented for optimal performance when the CPU
>> lists
>> multiple sse implementations. For example, should a CPU support sse4,
>> would I be limiting performance if I opted for OpenMP with -msse2, or
>> not?
>
> Some 32-bit builds need the latter. For a 64-bit build they produce the
> same result.
I find the former to work better than the latter on 32-bit systems.
Brad
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