[gmx-users] PME scalling

[Dmitry Kovalsky]

Hi there

I have a system with 25000 atoms and want to run a PME simulation on parallel
I have 4 dual athlons connected with fast ethernet
and when i setup 1ns simulation at one node (2cpu) it runs 1.5 days with 
perfect cpu loading 99.8% each 
but when I run at all 8 cpu's it runs 2.5 days! with 20% and 40% cpu usage one 
every node.
is it a problem of network speed?
The relevant part pf mdp file is
coulombtype         =  PME
optimize_fft        =  yes
pbc                 =  xyz
fourierspacing      =  0.12
pme_order           =  5
nstlist             =  10
ns_type             =  grid
rlist               =  0.9
rcoulomb            =  0.9
rcoulomb_switch     =  0
rvdw                =  1.5
vdwtype             =  cut-off

should I change   fourierspacing and pme_order as Erik proposed

or It would be better to use ReactionField?

I'm using near 40 ions in the system 

Thanks in advance

Sincerely yours,

Dima

Ph.D. Student Dmitry Kovalsky
Institute of Molecular Biology & Genetics
150 Akad. Zabolotnogo Street,
Kiev-143, 03143
UKRAINE

E-mail: dikov at imbg.org.ua
Fax:  +380 (44) 266-0759
Tel.: +380 (44) 266-5589