Re: [ccp4bb]: question about Linux-based crystallographic computing(fwd)

[Eric Bennett <ericb@pobox.com>]

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Anastassis Perrakis wrote:

> So, if you opt for that choice (as we do) then you really get much more from
> the Alpha architectures, in any respect I can think of.
> rem also that PC with multi-procs tend to cost as much as Alphas.
> 
> Last but not least, no matter what the benchmark sites say, in my experience
> Refmac is ~3 times faster in my ES40/667MhZ than in a PIII-850Mhz. Simply, I
> guess, the Alpha compilers for F77 are way better than g77. So unless you also
> get the pg or intel compilers and spend some (...) time to compile everything
> with them, at the end of the day the Alphas are faster for the
> usual-day-in-crystallography.

The Alphas are certainly still faster but the advantage is getting to be
quite marginal.  A single-processor 2 GHz P4 is something like ~90% the
speed of our 667 MHz XP1000 systems when running executables that I assume
are well optimized for both systems (for example, the precompiled SnB
binaries, and some other computational but noncrystallographic software
that we use).  When using the fairly lousy latest version of G77 things are
certainly worse; CNS is almost twice as fast on our Alphas as compared to a
2 GHz P4 when using G77 3.x.

Since a single-CPU P4 is a lot cheaper, it is a very stiff price to pay for
the Alpha to get that last bit of extra performance, assuming you have good
compilers on the PC.  For a variety of reasons we have still been choosing
to pay that extra price and go with the Alpha (except for testing PCs from
time to time), but it's getting to be a very close call.

-- 
Eric Bennett ( ericb@pobox.com ; http://www.pobox.com/~ericb )

Artists can color the sky red because they know it's blue.  Those
of us who aren't artists must color things the way they really
are or people might think we're stupid. -Jules Feiffer