[Wannier] wannier90 + vasp initial projections parallelism

[Giovanni Pizzi]

Dear Aron,
indeed, the calculation of overlaps and projections is done by the code 
interface, so for direct help of the VASP interface, you should address 
directly to the VASP developers (disabling the calculation of one part, 
or adding parallelism on the calculation of initial projections, should 
be easy, I believe).

If you want to use Quantum ESPRESSO, as Nicola suggested, the executable 
to run is pw2wannier90.x (and since all tutorials of Wannier90 are 
written with this interface in mind, you will already find instructions 
and example input files to pw2wannier90.x in the Wannier90 
tutorial/examples).
You will want to explicitly define write_amn and write_mmn in the input 
file to pw2wannier90.x to select whether to calculate these matrices 
(other options exist to choose whether to write the u_nk for Wannier 
function plotting [write_unk], etc.; see the source file 
PP/src/pw2wannier90.f90 inside the QE distribution, for instance).

Best,
Giovanni


On 01/13/2015 12:35 PM, Aron Szabo wrote:
> Dear Nicola,
>
> I meant to do separately the calculation of the overlaps (with the 
> unmodified code. This part seemed to scale with the cpu-s, and it 
> doesn't depend on the projections), and the calculations of the 
> projections that could be "parallelized" by running vasp many times 
> with selecting just a few projections in the input for each, and just 
> concatenate the results (and change the band indices). That's how I do 
> it now, and it works, but the overlaps are calculated in each case, 
> while they are identical, and it takes a lot of time unnecessarily, 
> making it impossible to go above a certain size (300 atoms approx.).
>
> Anyway, my next question would have been that how is it done in 
> quantum espresso. So thank you for your answer, I'm going to check 
> whether I could do all my tasks with quantum espresso. It seems to be 
> more practical in this respect then.
>
> And thank you for your offer to meet in person. I will probably use 
> the opportunity, and contact you in private to arrange the details.
>
> Best regards,
> Aron
>
> On 01/13/2015 12:00 PM, Nicola Marzari wrote:
>>
>> Hi Aron,
>>
>>
>> but without overlaps you won't have MLWFs? I guess you are just trying
>> to do "poor man's Wannier" via projections?
>>
>> Still, might be worth trying quantum-espresso, since those calculations
>> are parallelized. All plane wave codes are fairly similar, at the end...
>>
>> I'll be in ETHZ next week (wed/thu), so we could always catch up there.
>>
>>             nicola
>>
>>
>> On 13/01/2015 11:55, Aron Szabo wrote:
>>> Dear Wannier90 developers,
>>>
>>> I'm using vasp 5.3 and wannier90 2.0. I've noticed that the calculation
>>> of the initial projections for the wannierization in vasp is 
>>> sequential,
>>> it doesn't speed up with the increasing number of cpu-s. For large
>>> systems I'm calculating separately smaller sets of projections to
>>> emulate some parallelism, but there is a huge overhead from calculating
>>> the overlaps first in each case. It can take 1-2 days just to start
>>> calculating the projections when I have 2-300 atoms (1-2000 bands). So
>>> generating the projections can take more time than the actual
>>> wannierization. If the calculation of the overlaps could be somehow
>>> switched off, it would already solve this problem practically, because
>>> then the calculation of the projections would scale nicely, and the
>>> overlaps could be calculated in a separate run. I'm not good in 
>>> fortran,
>>> so I'm asking you whether it could be done maybe by just commenting out
>>> a few lines somewhere either in vasp's or wannier90's code, and if so,
>>> where is it exactly? I'm also interested if it is planned at all to
>>> parallelize the wannierization sometimes in the future, or is the
>>> problem itself something that's not possible to parallelize 
>>> efficiently?
>>>
>>> Thanks in advance,
>>> Aron Szabo
>>> PhD student at IIS, ETH Zurich
>>> _______________________________________________
>>> Wannier mailing list
>>> Wannier at quantum-espresso.org
>>> http://mailman.qe-forge.org/cgi-bin/mailman/listinfo/wannier
>>
>
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-- 
Giovanni Pizzi
Post-doctoral Research Scientist
EPFL STI IMX THEOS
MXC 340 (Bâtiment MXC)
Station 12
CH-1015 Lausanne (Switzerland)
Phone: +41 21 69 31124