[molpro-user] Question about Memory usage

Ulrich Wedig U.Wedig at fkf.mpg.de
Wed Mar 25 07:26:38 GMT 2009

I'm not an expert in operating systems, but my observation (and the
interpretation) is the following. My Linux system (SuSE Linux ES) uses
available free physical memory as a cache for I/O. The amount is given
in the output of the top command as 'cached'. In many of my molpro runs
I observe, that the memory allocated for the processes and 'cache'
(several GB) fill up the entire physical memory.
In the version 9 of SLES there was obviously a bug in this caching
mechanism. Physical memory was not freed appropriately when more memory
for processes was required. So, more and more swap space was used, and
the processes were slowed down due to swapping. This bug is corrected in
version 10 of SLES.

Ulrich Wedig

Kirk Peterson wrote:
> The one caveat is that the memory you specify in the input file is a  
> per process memory.  So if you run Molpro 4-way parallel the total  
> amount
> of memory would be 256MB x 4 = 1GB in your case.  Even with that,  
> though, I'm not sure why your job used all of your available memory.   
> The residence
> size of the executable is not all that big.  Can you do a "top" while  
> molpro is running to confirm that it is the process taking so much  
> memory?
> -Kirk
> On Mar 23, 2009, at 7:58 AM, zhendong zhao wrote:
>> Dear Molpro users,
>> I successfully compiled molpro 2008.1. Then I run bench tests on a box
>> with Intel CPU Q6600 and 4GB memory.
>> I try to run this job, bench/mpp_big_direct_lmp2.com using 4 cores,  
>> the
>> job consumed 4GB memory and filled the swap partition, so the
>> calculation is terribly slow. If molpro uses 2 cores, the speed is
>> fine, because it never use swap. My question is, the input file only
>> requests "memory,32,m", 32mw in 64bit OS is 32x8MB = 256MB, why the  
>> job
>> demands so many memory, how does molpro use memory?
>> Thanks in advance.
>> ZZ
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Dr. Ulrich Wedig                              Tel. 0711/6891535
Max-Planck-Institut fuer Festkoerperforschung FAX  0711/6891502
Heisenbergstr. 1
70569 Stuttgart                               U.Wedig at fkf.mpg.de

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