[Wien] Intel(R) Xeon Phi™ coprocessor
Peter Blaha
pblaha at theochem.tuwien.ac.at
Thu Sep 12 17:33:28 CEST 2013
Nice page, although of course what for wien2k matters is the performance
for lapack/blas calls for a diagonalization/matrix-matrix multiplication.
Anyway, you can see that
Intel Core i7-3930K @ 3.20GHz
is pretty high ranked and costs(560$) just a quarter of the top Intel
Xeon E5-2687W @ 3.10GHz (1930$), while its performance is only 15% less
than the top value.
And of course, this may change every couple of month ....
On 09/12/2013 03:46 PM, Michael Sluydts wrote:
> While I'm not sure how easily normal desktop benchmarks transfer to
> parallel processing through wien2k I usually look at the following
> benchmarks when comparing CPUs (and prices):
>
> http://cpubenchmark.net/high_end_cpus.html
>
>
> Best regards,
>
> Michael Sluydts
>
> Op 12/09/2013 15:43, Luis Ogando schreef:
>> Dear Prof. Blaha,
>>
>> Thank you very much for the explanations. They will be very useful !!
>> All the best,
>> Luis
>>
>>
>> 2013/9/12 Peter Blaha <pblaha at theochem.tuwien.ac.at
>> <mailto:pblaha at theochem.tuwien.ac.at>>
>>
>> This depends a lot on what you want to do and how much money you have.
>>
>> The single-core speed of a fast I7 is at least as good (or faster)
>> than most Xeons, and they are MUCH cheaper. So for all systems up
>> to 64-100 atoms/cell, where you need several k-points, a small
>> cluster of I7 cpus
>> /4 cores, or more expensive 6 core) (with GB-network and a common
>> NFS file system) is for sure the fastest platform and in
>> particular has by FAR the best price/performance ratio (One
>> powerful I7 computer may cost about 1000 Euro). For bigger
>> clusters, a drawback can be the large "space" to put all PCs on a
>> big shelf ....), but if you have less than 10000 Euros, this is
>> probably the best choice.
>>
>> However, Xeons can be coupled (2-4 Xeons) to a "single multicore
>> computer (eg. 16 cores)", which may work with mpi and can be used
>> to handle systems up to 200-300 atoms. They also can be bought in
>> small boxes and may fit in a single 19 inch cabinet. But of course
>> such systems are much more expensive. From what I said above it
>> should be clear, that it is completely useless to buy a "single 4
>> core Xeon computer".
>>
>> The next step would be to buy an Infiniband switch+cards and
>> couple your PCs with this fast network to a powerful multinode
>> mpi-cluster. Since the switch/cards are fairly expensive, on
>> usually takes here Xeons as platform. However, you need to know
>> how to install/configure the software properly. I've seen such
>> clusters even in computing centers, which were completely useless,
>> because the network/mpi was instable and jobs would crash randomly
>> every couple of hours .....
>>
>> Our strategy:
>> i) We have a GB-networked cluster with Intel I7 computers (which
>> we maintain our-self and this cluster includes also all the user-
>> workstations) and do all the calculations for systems up to 64
>> atoms/cell on these systems.
>> 2) For bigger systems we go to our University computer-center and
>> run there with a PBS queuing system. This has the advantage that
>> we do not need to care about the installation of the infiniband
>> network nor the mpi-infrastructure (but we use always intel-mpi
>> together with ifort/mkl).
>>
>>
>> On 09/11/2013 06:31 PM, Luis Ogando wrote:
>>
>> 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
>> <mailto:pblaha at theochem.tuwien.ac.at>
>> <mailto:pblaha at theochem.tuwien.ac.at
>> <mailto: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
>> <mailto:pblaha at theochem.tuwien.ac.at>
>> <mailto:pblaha at theochem.tuwien.ac.at
>> <mailto: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
>> <tel:%2B43-1-58801-165300> <tel:%2B43-1-58801-165300>
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>> <mailto:blaha at theochem.tuwien.ac.at>
>> <mailto:blaha at theochem.tuwien.ac.at
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>> <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 <tel:%2B43-1-58801-165300>
>> <tel:%2B43-1-58801-165300>
>> FAX: +43-1-58801-165982 <tel:%2B43-1-58801-165982>
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>> <mailto:blaha at theochem.tuwien.ac.at>
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>> --
>>
>> P.Blaha
>> --------------------------------------------------------------------------
>> Peter BLAHA, Inst.f. Materials Chemistry, TU Vienna, A-1060 Vienna
>> Phone: +43-1-58801-165300 <tel:%2B43-1-58801-165300>
>> FAX: +43-1-58801-165982 <tel:%2B43-1-58801-165982>
>> Email: blaha at theochem.tuwien.ac.at
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>> http://info.tuwien.ac.at/theochem/
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--
P.Blaha
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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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