[Pw_forum] parallel scaling in PWSCF

[carlo sbraccia]

Hi,

beware using the CVS version of PWSCF: the parallel Davidson has not yet 
been fully tested and seems to be buggy.
For this reason we are going to disable it until we shall be able to 
solve the problem. To avoid the serial bottleneck in the diagonalization 
you can use conjugate-gradient.

carlo

Andrea Ferretti wrote:

>Hi everybody,
>
>I am currently running a Copper surface with 140 Cu atoms + a molecule...
>the system has 1642 electrons and (due to metallicity) the calculation is 
>performed for 985 bands (few kpt, like 4)...
>due to the 11 electrons for each Cu atom, I have a huge number of bands in 
>a (relatively) small cell, and so a (relatively) low number of PWs respect 
>to nbnd.
>taking a look at the dimension of wfc, no problem with memory in 
>principle, even if, due to the weird 
>dimensions of the system, non-scalable memory is quite large, around 1Gb.
>
>on a IBM Sp5 machine I observed a severe limit in the scaling passing from 
>32 to 64 procs using both espresso 2.1.x and espresso 3.0...
>( anyway, I succeeded in performing a "relax" calculation for the system 
>!!!! )
>
>as far as I know, this problem might be connected to a serial part in the 
>diagonalization which has been parallelized in the current CVS version 
>(as already pointed out by Axel)...
>At the moment I am testing this CVS version against my system, I will let 
>you know the results as soon as possible...
>
>cheers
>andrea  
>
>
>  
>