[molpro-user] Shared memory question in CCSD(T) calculations

Manhui Wang wangm9 at cardiff.ac.uk
Mon Jun 24 11:44:27 BST 2013

Dear Jani,

If your Molpro job needs a certain amount of memory (eg. 8GB) to run 
with 1 core/process, then it will need N*8GB to run with N cores/processes.
The memory per core/process needed for your job will not be decreased 
when you run it in parallel.

Best wishes,

On 24/06/13 10:17, Jani Salo wrote:
> Dear Manhui,
> Thank you for your answer.
> However my question was a little bit different, briefly:
> If 1-core task require e.g. 8Gb of memory and my cores have access to 
> less than 8Gb, can I reduce memory demand per core by redistribution 
> it over N cores with lesser memory demand? If I can, what is the recipe?
> Thank you very much.
> Best,
> Jani.
> On Fri, Jun 21, 2013 at 2:12 AM, Manhui Wang <wangm9 at cardiff.ac.uk 
> <mailto:wangm9 at cardiff.ac.uk>> wrote:
>     Dear Jani,
>     The setting
>     memory, 1000, m
>     is for one core. If you use N cores, the total memory will be
>     N*1000*1000*1000 Words (ie,  N*1000*1000*1000*8 bytes).
>     For details, please refer to previous list
>     http://www.molpro.net/pipermail/molpro-user/2010-April/003723.html
>     Best wishes,
>     Manhui
>     On 20/06/13 11:49, Jani Salo wrote:
>>     Dear Molpro Users,
>>     I have specific question about how memory (or shared memory) is
>>     used in the parallel mode.
>>     I want to run an CCSD(T)/aug-cc-pVDZ calculation of uracil dimer
>>     on my small-cluster with 16 cores (with 64 GB of memory)
>>     It seems that such system needs more than 8GB of memory for
>>     1-core calculation, but it very slow, so when I'm trying to do a
>>     parallel calculation on 2 or 2^N cores
>>     the memory demand is not reduced by that factor. I've changed
>>     "memory, 1000, m" option back and forth, but it was not helpful
>>     either.
>>     (I've used compiled mpp-binary Molpro 2012.1 from the website)
>>     _So Is Molpro distribute used memory over processes or copied the
>>     same information? _
>>     How I can control this behavior?
>>     I've tried to use -G option (even that in manual written that "is
>>     no longer activated") but it was not helpful. I have not found
>>     the answer on this question in manual and other sources.
>>     Can one explain this issue?
>>     Thank you!
>>     Best,
>>     Jani.
>>     _______________________________________________
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>>     Molpro-user at molpro.net  <mailto:Molpro-user at molpro.net>
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>     -- 
>     -----------
>     Manhui  Wang
>     School of Chemistry, Cardiff University,
>     Main Building, Park Place,
>     Cardiff CF10 3AT, UK

Manhui  Wang
School of Chemistry, Cardiff University,
Main Building, Park Place,
Cardiff CF10 3AT, UK

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