ABINIT Discussion Forums

Hi,

Abinit 6.2.3 runs on a up-to-date Fedora system
(32 bits and with kernel 2.6.32-PAE).
The system has 6 GB RAM and 12 GB swap.

When I run the abinit job, it terminates because it cannot allocate
2779.477 Mb (see below for snippet from the log file).

How come this job cannot find 2779.477 MB (= 2.7 GB) ?

The 'top' command tells me that 90 % of the swap is not used
and 2 GB of RAM is free.

Am I facing here the limitation of a 32 bits version of the Linux OS?
If I replace the 32 bits OS with its equivalent 64 bits version,
would that help?

My PC has an Intel Core i7 CPU, which effectively shows as 8 CPUs.
Would parallelization with mpi on the localhost do any good to solve
this memory problem?

Thank you!
Rob.


Here is the snippet of the log file:

[...snip...]
=========================================================
P This job should need less than 2779.477 Mbytes of memory.
Rough estimation (10% accuracy) of disk space for files :
WF disk file : -1573.915 Mbytes ; DEN or POT disk file : 9.613 Mbytes.
=========================================================

Biggest array : f_fftgr(disk), with 9.6128 MBytes.
memana : allocated an array of 9.613 Mbytes, for testing purposes.

memana : ERROR -
Test failed to allocate 2779.477 Mbytes
It is not worth to continue
Action : modify input variable to fit the available memory.
or increase limit on available memory.

leave_new : decision taken to exit ...
=========================================================

You should first be aware that Abinit tends to underestimate memory requirements.

With a 32-bits OS, you can use up to 3Gb of memory. Going to 64 bits is interesting only if you have more physical memory.

In your case, using MPI will not help, since the resources available will not increase. You will probably need even more memory if you do so.

Hard to tell if the memory limitation is real or enforced by the 32 bit stuff. You can upgrade your system and recompile abinit as a 64 bit executable. Running in mpi might actually help if each of the threads is using less memory (can be handled by 32 bits) even though the total will be more (but still less than your 6 Gb).

Cheers

Matthieu

In any case, with a 32-bit Linux, the kernel will only be able to address 3Gb of physical memory at most. It is really worth going to 64-bit when you have more memory.