[Wien] Multicore on i7 iMac

[pluto at physics.ucdavis.edu]

Dear Prof. Blaha,

Thank you for the rapid response which allows me to start calculating some
bigger slab quickly!! After setting OMP_NUM_THREADS=4 program works on 4
cores (around 400% of the CPU in top) for the substantial amount of time.

I will test this setting for a while, and in the meantime make some
efforts to try k-parallel-mode, though I currently get some errors (see
below), probably related to the ssh access (explained in section 5.5.1 of
the Wien2k UG).

Regards,
Lukasz


x lapw1 -band -up -p
starting parallel lapw1 at Mon Apr 15 14:32:54 CEST 2013
->  starting parallel LAPW1 jobs at Mon Apr 15 14:32:54 CEST 2013
running LAPW1 in parallel mode (using .machines)
1 number_of_parallel_jobs
[1] 17208
The authenticity of host 'localhost (::1)' can't be established.
RSA key fingerprint is 50:c3:da:fa:0c:35:c5:aa:d1:b4:c1:52:a1:18:08:c2.
Are you sure you want to continue connecting (yes/no)? yes

^C





-------- Original Message --------
Subject: 	Re: [Wien] Multicore on i7 iMac
Date: 	Mon, 15 Apr 2013 08:16:11 +0200
From: 	Peter Blaha <pblaha at theochem.tuwien.ac.at>
Reply-To: 	A Mailing list for WIEN2k users <wien at zeus.theochem.tuwien.ac.at>
To: 	A Mailing list for WIEN2k users <wien at zeus.theochem.tuwien.ac.at>

As you could see from your "top" command, only 1 core is used.

The "simplest" thing is to set:

export OMP_NUM_THREADS=2 (or 4)    (a commented line is already in your
.bashrc after  "userconfig_lapw")

This will use 2 (4) cores for parts of WIEN2k which uses the mkl-library.
---------------------------
Next is k-parallel mode   (see UG for description), where you can use all
your cores.

We also have mpi-parallel, but I would not recommend it for a single mac,
unless you have a problem with just one k-point.

Please also notice the recent posting on the mailing-list about a
recommended compiler option for a Mac (-heap-arrays), otherwise you cannot
run wien2k on larger systems

Peter Blaha



From:pluto at physics.ucdavis.edu
Date:04/14/2013 07:48 PM
To:"A Mailing list for WIEN2k users" <wien at zeus.theochem.tuwien.ac.at>

Hello WIEN2k experts,

I have a very simple question.

Do I need to edit the .machines file for the multicore operation of the
Intel i7 Quad Core CPU?

My IT department (in FZ Juelich, Germany) has helped to compile Wien2k on
an iMac with i7 CPU. It works very nice, no problem to calculate 15 layer
slab. However, I have a feeling, that all is done on a single core, and
this is a real waste to time. I attach the screenshot of "top" program
under the terminal, with lapw1c doing 100 k-points for band structure.

Regards,
Lukasz



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