Hi Alex,

> I am planning to build or buy a 4-cpu linux cluster mainly to run ADF
> and
> Gaussian 03. I am wondering if anybody on this list can share some
> experiences regarding the use of Athlon or P4 based PCs for that
> purpose,
> or whether there is some sort of benchmarking available for the two
> processors. From what I gather on the internet, Athlon XP still seems
> to
> have the better FPU power, unless one can utilize the P4's SSE2
> extension
> to its instruction set. IIRC SSE2 is supported in the more recent linux
> kernels, but is it utilized in ADF and does ADF actually run faster on
> a
> P4 compared to an XP? Due to budget limitations I am currently looking
> at
> either a Xeon P4 system or four individual P4 or Athlon PCs strung
> together with 1 GB/s ethernet.
We have an Athlon based system, and it caused some real headaches in
terms of getting it stable. My feeling is that the quality of the
Pentiums is better in this respect, and I think it is worth taking into
account.

Regarding performance, ADF is currently being tested with the Intel
compiler, and results are quite promising. Performance seems to be on
the order of 30% faster, if I recall properly. This compiler is
optimized for Pentium chips, of course, and there is a reasonable
chance it will be supported for ADF in future. I think this will give
the Pentium the edge performance wise over the AMD.

>
> What is actually the bottleneck in a typical ADF calculation, say a
> geometry optimization of a 50-100 atom molecule? Is it processor speed,
> memory bus speed, disk IO, ...?
Typically you get close to 100% CPU load, so I would say the bottleneck
for ADF is the processor. It isn't disk IO or interprocessor
communication for the most part. An exception to this rule is Band:
Band is disk bound in a big way.

Regards,
Drew

========================================
  Dr. Drew McCormack (Kmr. R153)
  Afd. Theoretische Chemie
  Faculteit Exacte Wetenschappen
  Vrije Universiteit Amsterdam
  De Boelelaan 1083
  1081 HV Amsterdam
  The Netherlands

  Email cormack_at_chem.vu.nl
  Telephone +31 20 44 47623
  Mobile +31 6 483 21307
  Fax +31 20 44 47629
Received on 2003-06-03 15:35:45