[Wien] Intel(R) Xeon Phi™ coprocessor

[Peter Blaha]

I don't know what "latest" means. We use the latest one installed on our 
supercomputers (4.1.1.036)

I have not seen any significant change with mpi in the last years.

PS: I just got info that we have now a new ifort available for download ...

On 09/11/2013 05:00 PM, Laurence Marks wrote:
> Thanks.
>
> One thing I will add/ask concerning the parallelization, the latest
> impi seems to be substantially better -- have you tried it? I have not
> just noticed this with Wien2k, but I am told that others have seen
> improvements in other codes.
>
> On Wed, Sep 11, 2013 at 9:42 AM, Peter Blaha
> <pblaha at theochem.tuwien.ac.at> wrote:
>> Before buying a couple of new computers, I was asking myself the same
>> question and discussed this with some people of our computing departments.
>>
>> The conclusions:
>> a) potentially very good, but in practice very questionable, because for
>> most application you cannot get out the real speed (10 times faster than
>> an Intel I7). This is true, even for many lapack/mkl subroutines where
>> it "should" work better.
>> They told me to "wait", until the mkl becomes better (hopefully). I'm
>> not too optimistic, when you see how badly the mkl-parallelization of
>> multicore machines is working (2 cores is very good, but 4 or more is
>> already very bad).
>>
>> b) The nature of our problem (big eigenvalue problem): A "fast
>> processor" is useful only for large problems --> large memory.
>> You can buy Phi coprocessors now with quite some large memory, but then
>> they are terrible expensive (and 5 "normal" PCs are faster and cheaper)
>>
>> c) the hardware design has a VERY slow communication between main-memory
>> and Phi-memory. This makes also parallelization over several PHI-nodes
>> via mpi not really possible (if you need any significant data transfer,
>> like for an eigenvalue problem).
>>
>> Thus I did not buy it.
>>
>> However, if anybody has access and time to try out WIEN2k on PHis, I'd
>> would be very interested in getting feedback. (Maybe these
>> computer-people were not good enough ....)
>>
>> PS: I know from G.Kresse that they had some time ago (maybe 2 years ?)
>> an expert from NVIDIA with them. After 2 weeks of porting VASP to these
>> GPUs by this expert, VASP on the GPU was "almost as fast" as on an Intel
>> I7 processor.
>>
>>
>> On 09/11/2013 04:16 PM, Laurence Marks wrote:
>>> Anyone know if these will be viable with Wien2k (mpi, i.e. large problems)?
>>>
>>
>> --
>>
>>                                         P.Blaha
>> --------------------------------------------------------------------------
>> Peter BLAHA, Inst.f. Materials Chemistry, TU Vienna, A-1060 Vienna
>> Phone: +43-1-58801-165300             FAX: +43-1-58801-165982
>> Email: blaha at theochem.tuwien.ac.at    WWW:
>> http://info.tuwien.ac.at/theochem/
>> --------------------------------------------------------------------------
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>
>

-- 

                                       P.Blaha
--------------------------------------------------------------------------
Peter BLAHA, Inst.f. Materials Chemistry, TU Vienna, A-1060 Vienna
Phone: +43-1-58801-165300             FAX: +43-1-58801-165982
Email: blaha at theochem.tuwien.ac.at    WWW: 
http://info.tuwien.ac.at/theochem/
--------------------------------------------------------------------------