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

[Rafael R. Pappalardo]

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. 

Thanks for the attention.

Best regards,

Rafael
-- 
Dr. Rafael R. Pappalardo
Dept. Physical Chemistry, Univ. de Sevilla (Spain)
e-mail: rafapa at us.es