[gmx-developers] Assembler loops on Itanium2 Montecito.

[Rafael R. Pappalardo]

Dear all,
I am trying to install gromacs_cvs in a system with Itanium2 (Montecito) CPUs. 
Configuring without assembler loops seems to work but when I compile with 
assembler loops mdrun complaints about:

Configuring nonbonded kernels...
Testing ia64 CPU family...Unknown Itanium
You might want to test the speed without assembly kernels
by setting the NOASSEMBLYLOOPS environment variable.
Using single precision ia64 assembly kernels.

Looking at src/gmxlib/nonbonded/nb_kernel_ia64_single/nb_kernel_ia64_single.c 
I find that the test to recognize an Itanium2 assumes that the cpu_family is: 
0x1f (31). This value is correct for Madison Itanium2 but the Montecito's are 
0x20 (32). 

If I change the test and include the 0x20 family as Itanium2 the program seems 
to enter an infinite loop. The last lines in the md.log file is:

Configuring nonbonded kernels...
Testing ia64 CPU family...Itanium 2
Using single precision ia64 assembly kernels.

Removing pbc first time
Done rmpbc
There are 3000 flexible constraints

++++ PLEASE READ AND CITE THE FOLLOWING REFERENCE ++++
B. Hess, H. Saint-Martin and H.J.C. Berendsen
Flexible constraints: an adiabatic treatment of quantum degrees of freedom,
with application to the flexible and polarizable MCDHO model for water
J. Chem. Phys. 116 (2002) pp. 9602-9610
-------- -------- --- Thank You --- -------- --------


Initializing LINear Constraint Solver

++++ PLEASE READ AND CITE THE FOLLOWING REFERENCE ++++
B. Hess
P-LINCS: A Parallel Linear Constraint Solver for molecular simulation
J. Chem. Theory Comput. 4 (2008) pp. 116-122
-------- -------- --- Thank You --- -------- --------

After that the cpu time increases and the program never finish. The same test 
with the NOASSEMBLYLOOPS variable set in the environment end in less that 2 
minutes.

I have tried with gcc 4.1, gcc 3.4 and ifort 10.1 with the same results. I 
have access to two different machines one is running SLES 10 and the other 
some Redhat variation.

Any suggestion about how to discover what's going on?

Thanks a lot for the attention.

Rafael R. Pappalardo



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