[ODE] ODE slow on itanium?

Bill Sellers wis at mac.com
Wed Dec 6 13:22:03 MST 2006

Yup, I get more or less the same results each time (not exactly the  
same but as close as I've come to expect). For anyone who is  
interested and for my specific application the run times were:

Intel Xeon 5160 3GHz       icpc 1.224s
Intel Xeon 5160 3GHz       g++  1.803s
AMD Opteron 252 2.6GHz     g++  1.477s
AMD Opteron 250 2.4GHz     g++  1.702s
AMD Opteron 250 2.4GHz     icpc 1.859s
AMD Athlon MP 2000+ 1.7GHz g++  3.360s
Intel IA64 1.6GHz          icpc 3.465s
Intel IA64 1.6GHz          g++  4.919s

The last 6 were running some flavour of Linux and the first two were  
running MacOSX. These runs are all simulation only with no display  
whatsoever and very little i/o beyond loading up the program, reading  
a small data file and printing out the results. They all get 100% of  
a cpu when running.


On 6 Dec 2006, at 15:48, Thomas Yeh wrote:

> Did you verify the results from the Intel compiler binary visually?
> I had problems when I tried to use icc.
> Tom
> On Wed, 6 Dec 2006, Bill Sellers wrote:
>> Well gcc is certainly part of the problem. I've just recompiled
>> everything using Intel's own icc and icpc using the -fast flag and it
>> is quicker but it is still pretty slow. It was 3 times slower than
>> the Opteron with gcc, now its only twice as slow which is still
>> pretty disappointing (to me, since my University has just invested in
>> a great big multiprocessor cluster based on itanium chips). I've also
>> tried adding the -ftz flag which flushes denormals to zero on i64
>> systems (according to the icc man page anyway) but it makes almost no
>> difference at all so it's not that in my case.
>> Cheers
>> Bill
>> On 5 Dec 2006, at 21:57, Francois Beaune wrote:
>>> one thing to keep in mind is that itanium needs heavy
>>> assistance from the compiler. i don't know how good
>>> is gcc for itanium, but i suspect it is largely inferior to
>>> a native compiler for that processor.
>>> do you have access to the intel compiler for itanium?
>>> francois
>>> ----- Original Message -----
>>> From: "Andreas Fredriksson" <deplinenoise at gmail.com>
>>> To: "Bill Sellers" <wis at mac.com>
>>> Cc: "ode-list list" <ode at q12.org>
>>> Sent: Monday, December 04, 2006 20:38
>>> Subject: Re: [ODE] ODE slow on itanium?
>>>> On 12/3/06, Bill Sellers <wis at mac.com> wrote:
>>>>> Hi All,
>>>>> I've just been doing some benchmarking of my simulation on various
>>>>> processors and they all behave about as I expect except for a  
>>>>> truly
>>>>> dreadful showing on a recent 1.6GHz Itanium system. It's over 3
>>>>> times
>>>>> slower than an Opteron 252 which is hardly cutting edge  
>>>>> anymore, and
>>>>> over twice as slow as the Xeon 5160 in my MacPro. They are all
>>>>> compiled with gcc using the standard "-O3 -ffastmath" options.
>>>>> Anyone
>>>>> got any idea what's wrong since I don't think the Itanium  
>>>>> should be
>>>>> this slow...
>>>> Make sure you're not gettig denormals propagating through your
>>>> simulation; from what I've heard they're very slow on Itanium.
>>>> They're
>>>> also very slow on AMD and Intel hardware, unless by chance the
>>>> precision of the simulation is different enough that you're only
>>>> seeing the problem on the Itanium box.
>>>> Good luck,
>>>> Andreas
>>>> --
>>>> My other car is a cons.
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