[Wien] Intel(R) Xeon Phi™ coprocessor

[Luis Ogando]

Dear Prof. Blaha,

   Just for curiosity, what processor did you buy ?
   Is the Xeon family better than the i7 one for WIEN2k calculations ?
   All the best,
                       Luis


2013/9/11 Peter Blaha <pblaha at theochem.tuwien.ac.at>

> 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/<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/**
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