[Q-e-developers] Speed up of dos.x

[Gabriele Sclauzero]

The post-processing code PP/src/dos.f90 is rather simple and usually very fast and it can be run in serial mode (indeed it is not parallelized).
However, when it is executed on a very large system one can run into memory problems (and significant slow-down as well) because the charge and the wave functions are read even if they are not actually used (inside the call to PW/src/read_file.f90).
I see two very simple solutions to this problem, but I'm not sure that they don't know have any drawback, and I can't judge which is preferable from the code maintenance point of view.
1. modify read_file.f90 by adding an input variable that specifies if we need or not wave functions, charge, etc. This would require changes in all codes calling that subroutine.
2. just modify dos.f90 by replacing the call to read_file with those sections of read_file that are strictly needed. This might pose some issues of code maintenance.

I've tried the second solution and it seems to solve my problem, but I would like to get some advice from you.

Bests,

Gabriele

§ Gabriele Sclauzero, EPFL SB ITP CSEA
   PH H2 462, Station 3, CH-1015 Lausanne







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