Re: tuning of Atlas on x86/NUMA

I have dual socket quad-core Opteron 2350/2 Ghz - based server.

1) For single-threaded Atlas

For the current 3.8.2 I may use taskset or/and numactl utilities to
force processor affinity (and NUMA memory allocation) at the tuning
phase.

What should I use to be correct ?

I may use taskset/numactl simple for issuiing of the corresponding
makes.
Is it necessary to use

taskset -c <CPU_number> make build

IMHO, it's reasonable to use taskset/numactl for make check also -
right ?

BTW, I beleive I should use also -D c -DPentiumCPS=2000, right ?

It'll give the possibility to see on NUMA/cpu affinity influence.

I may insert taskset/numactl somewhere "more exactly" - but I don't
know where.

2) For pthreaded Atlas

The simplest practical (stupid :-)) ) idea to see on influence of
cache sharing (L3 for Opteron quad-core) is to prepare some shell
script where 8 (I have 8 cores) examplars of Atlas tuning will run
simultaneously.

i.e. something like
#! /bin/sh
numactl <parameters_for_core 1> make build >& >out_1 &  
numactl <parameters_for_core 2> make build >& >out_2 &
...
numactl <parameters_for_core 8> make build >& >out_1 &

Taking into account that building time is relative high, I think I may
neglect small difference in starting time.
I'll need then to have 8 copies of Atlas directories trees :-)  

In that case there will be 8 simultaneous tuning processses whcih will
share common L3 cache.

Is this "proposal" reasonable for particular case I have ?
(of course, better is to insert numactl somewhere more "exacrly").

FYI: I'm esepecially interesting in dgemm, which eats most of CPU time
of some our application.

Yours
Mikhail Kuzminsky
Computer Assistance to Chemical Research Center
Zelinsky Institute of Organic Chemistry
Moscow

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