[Pw_forum] P4HT problem?

[Paolo Giannozzi]

On Friday 09 July 2004 09:11, Dariusz Chrobak wrote:

> Do you have experience with running paraller version of the pw.x 
> on P4 HT processor? [...] CPU time is nearly equal to the CPU time
> for sequential version of pw.x. Do you have any comments?

From the manual:

   Note also that Beowulf-style machines (PC clusters) may have
   disappointing parallelization performances unless they have a
   decent communication hardware (at least Gigabit ethernet). 
   Do not expect good scaling with cheap hardware: plane-wave
   calculations are not at all an "embarrassing parallel" problem.

Lemon alert:

some multiprocessor motherboards for Intel CPUs have just one 
memory bus for all processors. This dramatically slows down any 
code doing  massive access to memory (such as PWscf and other
plane-wave codes) that runs on processors belonging on the same 
motherboard. Hardware produced by well-known brands and sold 
at premium price belongs to this category.

Paolo
-- 
Paolo Giannozzi             e-mail:  giannozz at nest.sns.it
Scuola Normale Superiore    Phone:   +39/050-509876, Fax:-563513 
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