[gmx-users] Performance in ia64 and x86_64

[Carsten Kutzner]

Hello Ignacio,

On Feb 25, 2011, at 10:25 AM, Ignacio Fernández Galván wrote:
> Well, I've compiled mdrun with MPI (with fortran kernels in the ia64), and run 
> my test system in both machines, with a single processor. The results are still 
> worrying (to me). This is a 500000 time step (0.5 ns) simulation with 1500 water 
> molecules, not a big system, but it still takes some hours:
> 
> x86_64: 3.147 ns/day
> ia64: 0.507 ns/day
> 
> 
> Is this difference normal? Am I doing anything wrong? what further data should I 


Some time ago I compared Itanium and x86 performances, see the fifth slide of this PDF: 

http://www.mpibpc.mpg.de/home/grubmueller/ihp/ckutzne/Talks/PDFs/kutzner07talk-optimizing.pdf

With Fortran kernels I got a performance of 0.31 ns/day for an 80,000 atom system
(with PME) on an Altix 4700, so your 0.5 ns/day for 1,500 waters seems too slow to me. 
What processor is this? Are you shure you are using the Fortran and not the C kernels?

Carsten