[Wien] Intel(R) Xeon Phi™ coprocessor
Michael Sluydts
michael.sluydts at ugent.be
Thu Sep 12 17:49:25 CEST 2013
Should probably also note with that page that the high end AMD CPUs are
typically much cheaper, but they tend to have double the cores with
nearly the same power usage per core (so double the power) compared to
an i7 or xeon, at continuous operation this can lead to a painful power
bill, possibly aggrevated by heat generation requiring more active
cooling (though I don't remember data on the temperatures).
Op 12/09/2013 17:33, Peter Blaha schreef:
> 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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>>> <tel:%2B43-1-58801-165982> <tel:%2B43-1-58801-165982>
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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>
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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>
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>>
>>
>>
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>
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