What virtual machine (Virtual Box, VMware, etc. [1])? Seems to matter
according to [2,3].
Since a virtual machine tends to be an operating system running on top
of another operating system (OS), there will most likely be a
performance loss to your calculations [4]. Perhaps the calculation will
run slower [disk caching due to lack of random access memory (RAM), CPU
sharing between both OS) or structures that can be calculated could be
limited by the loss of free RAM (two OS using RAM instead of just one OS
+ RAM used by virtual machine software].
TiC case is fine for first learning mpi parallel but is known that it
can be slower than just doing a serial calculation for it as it is too
small a case (e.g., to few nonequivalent atomic positions) [5,6].
Your statement below "... calculations take longer than in series ..."
seems to confirm this.
"... one processor for the variable OMP_THREAD (instead of 20 cores)
..." <- Don't confuse a thread and a core, they should be different
[7,8,9]. For example, look at the specifications for an i7-8700K
processor [10] which shows that Intel processor has # of cores as 6 and
# of threads as 12.
Is OMP_THREAD a special variable particular to your system? If not, you
might want to check your .bashrc (within the block created by
userconfig_lapw) and the WIEN2k 19.1 UG (section "5.5.3 How to use
WIEN2k as a parallel program" on page 86) [11] as a different
environmental variable might be needed.
username@computername:~$ grep THREAD ~/.bashrc
export OMP_NUM_THREADS=1
[1] https://en.wikipedia.org/wiki/Virtual_machine#Full_virtualization
[2]
https://superuser.com/questions/1035010/what-is-the-performance-difference-of-a-virtual-machine-vs-the-physical-host
[3]
https://www.researchgate.net/post/Why_there_is_a_performance_variation_between_physical_machine_and_virtual_machine_with_same_number_of_cores_and_memory
[4]
https://hetmanrecovery.com/recovery_news/how-to-speed-up-the-operation-of-a-virtual-machine.htm
[5]
https://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/msg05622.html
[6]
https://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/msg02976.html
[7]
https://bitsum.com/tips-and-tweaks/what-is-the-difference-between-a-thread-and-a-core/
[8]
https://www.intel.com/content/www/us/en/architecture-and-technology/hyper-threading/hyper-threading-technology.html
[9]
https://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/msg08702.html
[10]
https://ark.intel.com/content/www/us/en/ark/products/126684/intel-core-i7-8700k-processor-12m-cache-up-to-4-70-ghz.html
[11] http://susi.theochem.tuwien.ac.at/reg_user/textbooks/usersguide.pdf
On 8/19/2019 10:00 PM, Israel Omar Perez Lopez wrote:
Dear mailing list
I have a virtual machine with 20 cores running in linux mint (linux
recognizes that the computer has 20 cores divided in two nodes 10
each, however, there is only one physical node). How can I use Wien2k
to do parallel calculations in a virtual machine so the
parallelization uses the 20 cores. As far as I know, wien2k 19.1 has
three modes of parallelization: MPI, k-point and OMP (according to the
UG only for computers with less than 8 cores). I have already
installed intel parallel studio 2019 and wien2k but when I do the
userconfig the system only detects one processor for the variable
OMP_THREAD (instead of 20 cores). Since it is only one machine, what
is the best configuration in the .machines file to use the 20 cores?
Based on the UG I have tried three configurations for TiC in
.machines: 1) localhost:20, 2) MPI parallelization implemented as:
localhost, localhost, ....localhost 20 times, and 3) k-point
implemented as:
localhost
localhost
....
20 times
For the first and second case, the computations do not stop, it does
not even compute lapw0, so I have to cancel the job with cancel_lapw.
For the third case the calculations are carried out, but it seems that
the 20 cores do not work at the same time, they work one after another
and at the end, thecalculations take longer than in series. I checked
this with testpara1.
I would be glad if you could give a helpful comment on how to use the
20 cores in this machine.
Regards
Dr. Israel Pérez
Institute of Engineering and Technology
Department of Physics and Mathematics,
Universidad Autónoma de Ciudad Juárez
Av. del Charro 450 Nte., Col. Partido Romero,
Ciudad Juárez, Juarez Chihuahua. Mexico C. P. 32310
Tel: +52 (656) 688 4887
National Council of Science and Technology
Insurgentes Sur No. 1582,
Col. Crédito Constructor, C.P. 03940
Del. Benito Juárez, México D. F.
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