[Pw_forum] Memory usage in Quantum Espresso

[Krukau, Aliaksandr]

  Dear QE users,
   My desktop has Intel Core 2 Quad processor and 4GB RAM. However, 
when I run  Quantum Espresso (QE) 4.1, the biggest PWSCF jobs that I 
manage to run use about 200MB of RAM. For bigger systems or tighter 
cutoffs, the calculations crash with a segmentation violation. 
Moreover, if I use QE 4.2.1, the calculation crash even when I use more 
than ~100MB. So I am restricted to the quite small systems, especially 
if I use the latest 4.2.1 version. The user guide mentions that old 
compilers can reduce the size of the system that PWSCF can treat. But I 
use relatively new version 9.0 of Portland group Fortran compilers. If 
I run 'limit' command, it shows 'memoryuse unlimited; stacksize 
unlimited'.
    I apologize for the naive questions, but why can PWSCF use only a 
small fraction of my total RAM? Or the line "per-process dynamical 
memory" in the output file does not show the total required memory? Is 
there a way to run bigger calculations without using parallel execution 
(maybe by compiler flags etc.)?
  Best regards,
  Alex Krukau,
  Indiana University