[gmx-developers] Assembler loops on Itanium2 Montecito (again)

[Carsten Kutzner]

Rafael R. Pappalardo wrote:
> I don't have enough expertize to fix the problem with assembly loops on 
> Montecito. Following Carsten Kutzner suggestion I have compiled GROMACS 
> enabling fortran loops and obtained a considerable speed up with respect to 
> the C version. 
> 
> My suggestion is to include an specific test for Montecito CPUs and disable 
> the assembly loops similarly to what it's done when the NOASSEMBLYLOOPS 
> environment variable is set. I don't know if after the check for cpuid it's 
> still possible to dissable the use of assembly loops.
> 
> In this way Gromacs could run in a system with a mixture of Itanium2 
> processors. Running in Montecito processors will use fortran loops and on 
> non-Montecito ones the assembly loops without the user needing to change the 
> environment which cannot be feasible if there is a pool of cpus and you don't 
> know in advance which type of processor will run the job. 
Hi Rafael,

why don't you disable the assembly code at install time then? This way 
Gromacs would run on all Itanium CPUs, regardless if Montecito or not.

./configure --disable-ia64-asm --enable-fortran --enable-mpi

Hope that helps,
  Carsten

> 
> Thanks for the attention.
> 
> Best regards,
> 
> Rafael

-- 
Dr. Carsten Kutzner
Max Planck Institute for Biophysical Chemistry
Theoretical and Computational Biophysics Department
Am Fassberg 11
37077 Goettingen, Germany
Tel. +49-551-2012313, Fax: +49-551-2012302
http://www.mpibpc.mpg.de/research/dep/grubmueller/
http://www.gwdg.de/~ckutzne