[Wien] Would like to have some guidance from you

Thu Jul 7 10:56:15 CEST 2011

Thank you very much for the detailed explanation again Professor Blaha.
I will follow your suggestion and stop the current calculation, and starting from the simple cases with a lower RKmax.

PS: the cpu usage for the lapw1c is mostly at around 100% and the memory at around 77% in 'top' 

In the case.output1dn(up) I can see that the CUP time in interstitial (total) 15.44(15.29), and the cpu time in dstart: 104.55(103.89) - are we talking about the wall time is the dstart time? (I can not see anywhere says 'wall-time' in both files)- so this means my computer does not have enough memory (for this calculation)?

Thank you very much for your time.

kind regards,
Qiwen

------Original Message------
From:"Peter Blaha"<pblaha at theochem.tuwien.ac.at>
To:"A Mailing list for WIEN2k users"<wien at zeus.theochem.tuwien.ac.at>
Cc:
Subject:Re: [Wien] Would like to have some guidance from you
Date:07/07/2011 09:02:27 AM(+0200)
>As a beginner, you need to gain experience.
>
>So first start with pure A2BO4.  Does it run properly, check timings,...
>Then create first a smaller supercell, eg. a 2x2x1 cell. Does it run ?
>timings (4 times as many atoms, --> without iterative diag. ~ 64 times
>as long cpu-time in lapw1. However, in the supercell you can use 4 times
>less k-points, s the total effort does NOT increase that much.
>
>For the large cell: use the   top  command to check the performance of
>lapw1 or lapw2. In particular you should see of it uses the cpu by nearly
>100 (or 200 when OMP_NUM_THREAD=2) %, or it does not becuase it does not
>have enough memory and "pages".
>
>Also check the timings listed in case.output1up/dn. Is the cpu-time and wall-time similar ?
>If wall-time is much larger, your computer does not have enough memory.
>
>k-points: You heard at the workshop about k-points: metal-insulator or small-large cells.
>most likely I would not start out with so many k-points, but I don't know the details
>of your system. Of course 50-kpoints will run 4 times faster than 200 k.
>
>Another hint: For large cells you do not want to start out with RKMAX=7 (the default).
>Start the calculation with RKMax=6 or even 5.5. Run to scf, it should be MUCH faster
>(10-100 times !!!), but then don't stop, but increase RKMax and compare eg. the forces
>on all atoms, magnetic moments, DOS, (... what ever you are interested in) to find a
>reasonable RKMAX.
>
>And finally: For these large cells, iterative diagonalization should be used.
>
>I guess the most important message is: Start out with smaller problems. Experiment
>with parameters like k-points, RKmax, -it to get experience.
>
>Of course, a modern PC (or 4 of them for k-parallel runs) will help. But checkout the
>real bottleneck (memory ?) before.
>
>Am 07.07.2011 02:58, schrieb Dr Qi Wen YAO:
>> Dear professor Blaha and Wien2k users,
>>
>> Thanks to the Wien2k Workshop, now that I can do some proper calculation but since i am new to Wien2k and I would like to have some guidance in my current calculation.
>>
>> I am doing a supercell (3x3x1) calculation (for publishing quality) to a layered structure perovskite A2BO4 compound. It is of K2NiF2 structure (SG I4/mmm), its resistivity is at around 0.001 Ohm-m at room temp so it is semi-conductive.
>>
>> Half of the "A" atoms (A atom is Sr in this case, and the B atom is Co) are replace by an Rare Earth atom so the whole supercell is of 90 atoms in size in my struct file. The original unit cell parameters were a=b=3.8 Amstrong and c=12.3 Amstrong.
>>
>> I am using a PC with 2 core Xeon 2.4GHz, 4G RAM running latest Susie, latest Wien2k and ifort11.
>>
>> The calculation is Spin Polarized (and not an anti-ferromagnetic as I know that this compound is ferromagnetic), I used 200 k-points for the current calculation.
>>
>> The initialization seems working fine (thanks to professor Blaha's guidance in the workshop).
>>
>> Now it seems that the calculation is a bit too much for this computer - it runs painfully slow and after two days, it only just displays to me two lines: "LAPW0 END" and "LAPW1 END".
>>
>> I am wondering: for this calculation, can I use less k-points say 50 (as it is a big cell) and the result would still be good enough for paper publishing?
>>
>> What kind of speed up do I expect if I am to use a 50 k-pints instead of 200 k-points?
>>
>> Would you think that a computer with i7 core and 16GB of RAM would be able to run this calculation without too much trouble (I am trying to convince my boss to purchase a new PC for me for WIEN2k)?
>>
>> Any comments/feedback would be greatly appreciated.
>>
>> Thank you for your time.
>>
>> kind regards,
>> Qiwen
>>
>> **********************************************************
>>
>> Dr QiWen YAO
>>
>> JSPS Fellow
>> Multifunctional Materials Group
>> Optical and Electronic Materials Unit
>> Environment and Energy Materials Research Division
>>
>> National Institute for Materials Science
>>
>> 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047, Japan
>> Phone: +81-29-851-3354, ext. no. 6482, Fax: +81-29-859-2501
>>
>> **********************************************************
>>
>> _______________________________________________
>> Wien mailing list
>> Wien at zeus.theochem.tuwien.ac.at
>> http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien
>
>-- 
>
>                                       P.Blaha
>--------------------------------------------------------------------------
>Peter BLAHA, Inst.f. Materials Chemistry, TU Vienna, A-1060 Vienna
>Phone: +43-1-58801-15671             FAX: +43-1-58801-15698
>Email: blaha at theochem.tuwien.ac.at    WWW: http://info.tuwien.ac.at/theochem/
>--------------------------------------------------------------------------
>_______________________________________________
>Wien mailing list
>Wien at zeus.theochem.tuwien.ac.at
>http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien

**********************************************************

Dr QiWen YAO

JSPS Fellow
Multifunctional Materials Group
Optical and Electronic Materials Unit
Environment and Energy Materials Research Division

National Institute for Materials Science

1-2-1 Sengen, Tsukuba, Ibaraki 305-0047, Japan
Phone: +81-29-851-3354, ext. no. 6482, Fax: +81-29-859-2501

**********************************************************