[Pw_forum] ifc/linux allocation of more than 2 GB dynamical memory

[Konstantin Kudin]

 Dear Nicola

 Please read the thread from February "Error encountered while attempting to
allocate a data object."
In this post Serguei Patchkovskii explained how to maximize RAM under linux:
http://www.democritos.it/pipermail/pw_forum/2004-January/000825.html

 In short, it appears that static linking of everything (mkl included!!!) could
give more RAM. Since mkl 6.0 does not link this way, you need to use mkl 5.2

 Konstantin

--- Nicola Marzari <marzari at MIT.EDU> wrote:
> 
> 
> Dear All,
> 
> we have recently realized that there is an issue running large jobs
> on Linux machines, and I was wondering if anyone had some suggestions.
> 
> This is the problem: if a fortran code running under Linux
> (Red Hat 9) and using ifc (7.1) and mkl (6.0) tries to allocate
> a number of arrays that total over 2 GB, it ends with a runtime error.
> 
> This happens no matter the amount of dynamical memory physically
> available (we tested this on a machine having ~4GB RAM), and happens
> exactly at the point in which the array that is being allocated
> overshoots 2GB .
> 
> The Intel webpage has a comment somewhere mentioning this limitation,
> suggesting it is related to where the kernel allocates space for the
> linked libraries, but we have had no success trying their suggestions
> (e.g. compiling -static).
> 
> In practice, this limitation is even more serious, since a running
> code (e.g. CP) that allocates ~< 2GB will only use, in runtime, an
> average value that is smaller (~1.25GB).
> 
> Any helpful suggestions would be very welcome,
> 
> 
> 			nicola
> 
> ---------------------------------------------------------------------
> Prof Nicola Marzari   Department of Materials Science and Engineering
> 13-5066   MIT   77 Massachusetts Avenue   Cambridge MA 02139-4307 USA
> tel 617.4522758  fax 617.2586534  marzari at mit.edu  http://nnn.mit.edu
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