HI Ross:
I believe Amber users (and others, if they come across) should be grateful for this enlightening answer. Thanks for taking time to explain in such details
francesco
--- On Fri, 5/30/08, Ross Walker <ross.rosswalker.co.uk> wrote:
> From: Ross Walker <ross.rosswalker.co.uk>
> Subject: RE: Fw: RE: AMBER: MKL libraries/Amber10
> To: amber.scripps.edu
> Date: Friday, May 30, 2008, 3:41 PM
> > If its is MKL that makes the problem (on different
> hardware, by Cenk and
> > me), why not compiling Amber10 with ifort + ACML or
> GOTO libraries? Is any
> > indication how to set the congif file?
>
> Last time I checked GOTO was basically a cut down BLAS
> library designed to
> get very high linpack numbers and lacked any of the real
> useful stuff. This
> may have changed. Note it is actually LAPACK that we really
> need which
> obviously makes use of a lot of BLAS calls so one could
> perhaps use the
> lapack code included in AMBER and link it to GOTO blas but
> I don't know how
> useful this will be.
>
> As for ACML last time I looked at it (albeit a couple of
> years ago now) it
> seemed to have largely forgotten that double precision
> arithmatic exists.
> All the vector functions were single precision and I
> don't recall it having
> any of the matrix diagonalization routines in there so
> again not very
> useful. However, this may have changed so perhaps we could
> consider adding
> ACML support. Maybe if NSF awards an AMD based machine to
> SDSC I'll do it to
> earn some kudos ;-).
>
> > In previous mail Ross said that MKL will speed up QMMM
> by a large (not
> > minor) margin.
>
> This will of course depend on the QM system size. For less
> than 30 atoms or
> so there will be almost no difference, for 30 to 50 atoms
> it will be minor
> and for >50 atoms it will be a large difference so the
> importance of MKL is
> a function of what you want to run... <sigh> nothing
> is ever simple ;-).
>
> > As far as I know ACML are equivalent BLAS, and perhaps
> GOTO
> > is even better than MKL or ACML.
>
> The key routines for QMMM are vdinvsqrt, vdexp, vdsqrt,
> vdcos, dspev,
> dspevd, dspevr, dsyev, dsyevd and dsyevr.
>
> The first 4 are vector math functions and not strictly
> lapack routines.
> There is also not a consensus on the interface for such
> routines so GOTO
> would be no use here. ACML might help if it does double
> precision vectors.
> In fact looking at the documentation:
> http://developer.amd.com/assets/acml_userguide.pdf
>
> It does vectored cosine, vectored exponential and vectored
> log but AMD seem
> to have forgotten that people might want to do vectored
> sqrt or inverse
> sqrt. They support vectored power (to a float) but only in
> single precision
> :-(. And that probably doesn't make use of specialist
> sqrt hardware anyway
> even if you do it to the power 0.5 so that's probably
> not much good. So for
> vector math ACML would appear to be pretty useless.
>
> It at least looks like the lapack implementation is
> complete so this might
> help a bit - the threading might also help some for matrix
> diagonalizations
> although one would have to check.
>
> Although as usual we see that the marketing department does
> not live in the
> real world:
>
> "ACML's aggressively tuned OpenMP versions mean
> that you don't have to worry
> about managing sophisticated threading models or complex
> debugging. Whether
> you are using dynamic or static linking, Windows, Linux or
> Solaris 32- or
> 64-bit, multi threading just works. "
>
> Great.... for single cpu non-mpi code. If you are using MPI
> this sort of
> threading is just a complete pain...
>
> Just my 3c.... (my prices are going up due to the cost of
> oil...)
>
> All the best
> Ross
>
>
> /\
> \/
> |\oss Walker
>
> | Assistant Research Professor |
> | San Diego Supercomputer Center |
> | Tel: +1 858 822 0854 | EMail:- ross.rosswalker.co.uk |
> | http://www.rosswalker.co.uk | PGP Key available on
> request |
>
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>
>
>
>
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Received on Sun Jun 01 2008 - 06:08:12 PDT
