[DFTB-Plus-User] large-scale calculations_output overflow records and "cannot allocate memory error message"

[Ben Hourahine]

Hello Hafid,

for dense eigensolvers and an sp basis, the memory cost for the linear
algebra is approximately 2 - 4 times the square of

[ nAtoms * 4 basis * ~4 bytes if a real calculation (or 8 * number of
k-points for complex) ]

which for 1000 atoms is approaching 1Gb, while for your 32000 atoms
would be  about 800 Gb. If you have a distributed computer with for
example ~4 Gb per core that would require around 200 processors to store
the problem.


Instead, if your calculation is suitable, the ELSI sparse solvers have
much lower memory requirements (being ~ linear instead of proportional
to the square of the number of atoms). You could try either the NTPoly,
OMM or PEXSI solvers but with the Sparse = Yes option enabled. They each
have different pre-factors for memory requirement depending on their
settings. (OMM is intended for insulators, NTPoly will work for smaller
gaps, and PEXSI runs for everything but has a larger time prefactor for
3D systems). See the preprint

https://arxiv.org/abs/1912.13403

for a discussion of some of this.

Regards

Ben

On 05/06/2020 07:36, khalfoun hafid via DFTB-Plus-User wrote:
> Dear Ben,
> I try to calculate the electronic band structure for a large system (
> 32000 atoms of  Carbon) .
>
> Unfortunately I meet the output overflows record similarly as already
> been discussed
> https://mailman.zfn.uni-bremen.de/pipermail/dftb-plus-user/2018/002794.html
> <https://eur02.safelinks.protection.outlook.com/?url=https%3A%2F%2Fmailman.zfn.uni-bremen.de%2Fpipermail%2Fdftb-plus-user%2F2018%2F002794.html&data=02%7C01%7Cbenjamin.hourahine%40strath.ac.uk%7C8f3c2e12d858443d588508d8091aec43%7C631e0763153347eba5cd0457bee5944e%7C0%7C0%7C637269358994438836&sdata=v4rB%2FFypjG9zUdIbonmNO1U3RMbSQig3G1ZFU%2BNLRTw%3D&reserved=0>
>
> I've desactivated the writing of the dftb_pin.hsd file in the parser
> options ( as recommanded  in
> https://mailman.zfn.uni-bremen.de/pipermail/dftb-plus-user/2018/002795.html
> <https://eur02.safelinks.protection.outlook.com/?url=https%3A%2F%2Fmailman.zfn.uni-bremen.de%2Fpipermail%2Fdftb-plus-user%2F2018%2F002795.html&data=02%7C01%7Cbenjamin.hourahine%40strath.ac.uk%7C8f3c2e12d858443d588508d8091aec43%7C631e0763153347eba5cd0457bee5944e%7C0%7C0%7C637269358994438836&sdata=ebCExFnJaKBsfKCLAeWoKif8SYj31JMRbALJv6e1G3k%3D&reserved=0>
> )
>
> , but the problem of the non ability allocation memory still persist
> even I reach the limit of the required memory in the calculating
> machine. http://www.ceci-hpc.be/clusters.html#lemaitre3
> <https://eur02.safelinks.protection.outlook.com/?url=http%3A%2F%2Fwww.ceci-hpc.be%2Fclusters.html%23lemaitre3&data=02%7C01%7Cbenjamin.hourahine%40strath.ac.uk%7C8f3c2e12d858443d588508d8091aec43%7C631e0763153347eba5cd0457bee5944e%7C0%7C0%7C637269358994448837&sdata=Y%2FY6U2c6WcfUpz2MW7hHneNjd%2FB6SX%2Fpxdhn7P5oMJA%3D&reserved=0>
>
> what should I do  ?
> Using another machine with greater amount of RAM ?
>
>  
>
> thanks ,
> Hafid
>
>
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-- 
        Dr.  B.  Hourahine,  Senior  lecturer
            SUPA, Department  of  Physics,
             University  of  Strathclyde,
              John  Anderson  Building,
          107 Rottenrow, Glasgow G4 0NG, UK.                    
  +44 141 548 2325, benjamin.hourahine at strath.ac.uk

The  Department is  a partner  in SUPA,  the Scottish
            Universities Physics Alliance

The University  of Strathclyde  is a  charitable body,
       registered in Scotland, number SC015263

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