[Wien] Intel(R) Xeon Phi™ coprocessor
Michael Sluydts
michael.sluydts at ugent.be
Thu Sep 12 15:46:50 CEST 2013
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>
> FAX: +43-1-58801-165982
> <tel:%2B43-1-58801-165982> <tel:%2B43-1-58801-165982>
> Email: blaha at theochem.tuwien.ac.at
> <mailto:blaha at theochem.tuwien.ac.at>
> <mailto:blaha at theochem.tuwien.ac.at
> <mailto: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 <tel:%2B43-1-58801-165300>
> <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>
> FAX: +43-1-58801-165982 <tel:%2B43-1-58801-165982>
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