charmm scalability on 2.4 kernels

Eray Ozkural (exa) erayo at
Sat Jan 5 13:55:42 PST 2002

On Saturday 05 January 2002 20:10, Steve Fellini wrote:
> Hi All,
> Many of our users run charmm dynamics using Ewald/PME calculations,
> which require 3D FFTs.  When run in parallel on a cluster, these
> calculations scale moderately well to around 2-4 nodes (4-8
> processors) when run on either nodes on a Myrinet network, or on nodes
> running on fast ethernet with Linux 2.2.16 kernels with Josip
> Loncaric's tcp fix (see
> However for nodes running on ethernet with Linux 2.4.12 (i.e., without
> the tcp fix) scalability is very poor - so much so that there's no
> point in running on more than one node (see
> and image005.gif).

This is rather surprising, I'd expect 2.4.x to actually improve upon 2.2.x. 
It was said before on this list that 2.4 already incorporates TCP fixes. Has 
anybody met a similar situation before?


Eray Ozkural (exa) <erayo at>
Comp. Sci. Dept., Bilkent University, Ankara
GPG public key fingerprint: 360C 852F 88B0 A745 F31B  EA0F 7C07 AE16 874D 539C

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