[Wien] Installation of wienk

[Gavin Abo]

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 at 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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