[Pw_forum] memory

[Stefano Baroni]

Dear Jaita,

the "mistery" should only arise for a gamma-only calculation. In this 
case the number of plane waves, strictly speaking, remains roughly the 
same, but only half of them are really used because, due to 
time-reversal invariance, wavefunctions at k=0 can always be chosen to 
be real. i.e. the number of PW's is the same, but the number of 
plane-wave coefficients (which is what matters memory-wise) is halved.

Stefano

On Apr 16, 2005, at 1:01 PM, Jaita Paul wrote:

> Dear all,
>
> Before running pw.x calcs i gave a check on the memory estimate of the
> file.with 3 k points the estimated mem was 5.2 GB for a unit cell with 
> 91
> atoms-when i reduce the k-points to a single(gamma)point then also the
> estimated mem remains the same. the no. of plane waves reduces to
> half(from 31000 to 16000) when i change the k point mesh.i cannot 
> figure
> out the mistake....
> can anyone help me?cud this arise out of wrong input atomic coords?
>
> regards,
> Jaita.
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---
Stefano Baroni    ---  SISSA  &  DEMOCRITOS National Simulation Center
via Beirut 2-4 34014 Trieste Grignano / [+39] 040 3787 406 (tel) -528 
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