NEB: number of replicas, cpus and input files

Jörg Saßmannshausen j.sassma... at
Wed Nov 23 23:05:47 UTC 2011

Dear all,

I am a bit confused. 
When I am running a frequency calculation or a NEB calculation, I can specify 
the number of replicas (NUMBER_OF_REPLICA) and the number of processors 
(NPROC_REP) in the MOTION section. Now, lets say I got 32 cores on my hands 
and I got 17 files which I want to use for the NEB calculation. Now, my 
understanding was that I could run say 8 replicas and each replica is using 4 
cores. That would add up to the 32 cores I have alltogether. However, that 
does not work out. It appears I got to use 32 replicas and 32 cores for all 
32 cores I have available. What is the relationship between replicas and 
cores (in the input file) with the cores I have available on the machine (an 
in relation to the number of coordinate files I have). A similar observation 
was made for a frequency calculation. 

I seem to have somehow a wrong understanding here :-/

All the best from a foggy London


Jörg Saßmannshausen
University College London
Department of Chemistry
Gordon Street

email: j.sassma... at

Please avoid sending me Word or PowerPoint attachments.

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