[MITgcm-devel] [MITgcm-cvs] MITgcm/tools/build_options CVS Commit

[David Ferreira]

On 4/9/10 7:07 PM, Menemenlis, Dimitris (3248) wrote:
> Pierre and I ended up wasting a day because of this minor issue.  Specifically, this morning instead of looking at model results we spent time debugging an optfile.
Come on, really ? you are going for the guilt card. All that time and 
science lost because of
a "buggy" optfile ...
this could sound sad, but the problem is explained in the NAS webpage, 
and more importanly,
I clearly mentioned this issue BEFORE checking in the otpfile, and I 
received a "go".
BTW, there is no bug in this optfile.
> If objective is to provide as smooth an initial experience as possible, then we need to change to SSE4.1, with comments in optfile that 4.2 and 4.3 are available and possibly faster on some of the nodes.
Clearly, this is useless. If people were reading comments in the 
optfile, they wouldn't spend a
day submitting to the "normal" queue executables compiled with 
-xSSE4.2.... (ok, sorry but
this one was too tempting ... )

I get you are annoyed by the time lost, but the fact is there are 2 (and 
maybe 3 ?) queues
on pleiades. People should get this information somewhere (not just 
because of the executable
issue). My feeling is that most (100% ?) of the  new MITgcm users going 
to NAS will start
with help from someone (at MIT or JPL), this could be the way.

david


> Dimitris
>
> On Apr 9, 2010, at 2:42 PM, David Ferreira wrote:
>
>    
>> Dimitri,
>> My reasoning was more or less the opposite of yours: with -xSSE4.2, if
>> someone
>> makes the mistake of submitting to queue "normal", he will get an error
>> message
>> and realize there is an issue. BTW, the message is not really criptic,
>> (+documented on
>> the NAS webpage+comments in the optfile):
>>
>> Fatal Error: This program was not built to run on the processor
>> in your system. The allowed processors are: Intel(R) processors
>> with SSE4.2 and POPCNT instructions support.
>>
>> With xSSE4.1 by default, most people would not realize they could benefit
>> from running on normal_N with xSSE4.2 (and in my case I noticed a
>> significant
>> speed up, I can't remember exactly how much though !).
>> Is it not the case for you ?
>> david
>>
>>
>>
>> On 4/9/10 2:07 PM, Art Lazanoff wrote:
>>      
>>> a few additional notes:
>>>
>>> ifort v11.1 supports -xSSE4.1 and -xHost but not earlier compilers.
>>>
>>> Use of -xHost is interesting if and only the code is to be run on the
>>> same processor family (harpertown or nehalem, etc) as the code is
>>> compiled on. -xHost retrieves the CPUs feature set if possible. The
>>> Pleiades front-ends are currently Harpertown. One solution is to run a
>>> PBS job to compile the code.
>>>
>>> At the moment, NAS PBS offers Harpertown queues (-q normal) and a
>>> Nehalem queue (-q normal_N). The next assortment of nodes is due to
>>> arrive in a few weeks and these are Westmeres. We'll likely have
>>> another queue forthese.
>>>
>>> So, Dimitris, the answer to your question from earlier today about
>>> which CPUs you ran on can be determine by which queue you submitted
>>> the job to.
>>>
>>> Sincerely,
>>>
>>> Art
>>>
>>> *****************************************************************************
>>>
>>> Art Lazanoff                                     NASA Ames Research
>>> Center
>>> Senior Scientific Consultant                       Mail Stop 258-6
>>> Arthur.S.Lazanoff at nasa.gov  (650) 604-1687        Moffett Field, CA
>>> 94035-1000
>>> *****************************************************************************
>>>
>>>
>>> --------------------------------------------------
>>> From: "Menemenlis, Dimitris (3248)"<Dimitris.Menemenlis at jpl.nasa.gov>
>>> Sent: Friday, April 09, 2010 10:51 AM
>>> To:<mitgcm-devel at mitgcm.org>
>>> Cc: "Lazanoff, Arthur S. (ARC-AFS)[COMPUTER SCIENCES CORPORATION]"
>>> <arthur.s.lazanoff at nasa.gov>
>>> Subject: [MITgcm-devel] [MITgcm-cvs] MITgcm/tools/build_options
>>> CVS     Commit
>>>
>>>        
>>>> David, can I make SSE4.1 the default in linux_ia64_ifort+mpi_ice_nas
>>>> with a comment that 4.2 and 4.3 is also available on some of the
>>>> newer processors.
>>>>
>>>> 4.1 is the lowest common denominator.  That way new pleiades users,
>>>> e.g., Pierre Rampal, don't end up with cryptic error messages when
>>>> they try to use the default optfile.
>>>>
>>>> Also, according to Art Lazanoff, there is probably not much speed
>>>> up to be expected from 4.2 and 4.3 over 4.1.
>>>>
>>>> Let me know, Dimitris
>>>>
>>>>
>>>>          
>>> _______________________________________________
>>> MITgcm-devel mailing list
>>> MITgcm-devel at mitgcm.org
>>> http://mitgcm.org/mailman/listinfo/mitgcm-devel
>>>        
>>      
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