[gmx-users] Performance in ia64 and x86_64
Ignacio Fernández Galván
jellby at yahoo.com
Fri Feb 11 13:33:28 CET 2011
I'm compiling and testing gromacs 4.5.3 in different machines, and I'm wondering
if it's normal that the ia64 is much slower than the x86_64
I don't know full details of the machines, because I'm not the administrator or
owner, but /proc/cpuinfo says:
ia64 (128 cores): Dual-Core Intel(R) Itanium(R) Processor 9140N
x86_64 (16 cores): Intel(R) Xeon(R) CPU E5540 @ 2.53GHz
Just looking at the GHz, one is 2.5 and the other is 1.4, so I'd expect some
difference, but not a tenfold one: with 8 threads (mdrun -nt 8) I get 0.727
hours/ns on the x86_64, but 7.607 hours/ns on the ia64. (With 4 threads, it's
1.3 and 13.7).
I compiled both cases with gcc, although different versions, and default
options. I had read assembly or fortran kernels could help with ia64, but
fortran is apparently incompatible with threads, and when I tried with assembly
the mdrun seemed stuck (no timestep output was written). Is this normal? Is
there something else I'm missing?
Also, in the x86_64 system I get much lower performance with 12 or 16 threads, I
guess that could be because of the cores/processors, but I don't know what's the
exact configuration of the machine. Again: is this normal?
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