Hello Erik,

> It's strange that code without "-xHost" does not run on the head node. What
> other compiler options are there? The only reason I can see is that the
> Intel compiler has been installed in a special way to use additional
> compiler flags, and these flags make the code not work any more on Sandy
> Bridge.
It is some runtime detection that fails. I get:
--8<--
Please verify that both the operating system and the processor support Intel(R) 
F16C instructions.
--8<--
and adding -xHost complains that "icc: command line warning #10121:
overriding '-xCORE-AVX-I' with '-xHost'" so it seesm as if some vectorization 
is enabled by the cray cc wrapper.

> To my knowledge, the processors accept the same machine instructions. The
> CPU tuning might be different.
Is this also true for vectorization? Or maybe this really is just a
lack of OS support for the AVX registers on the login nodes. -xAVX
seems to work fine and the only difference (according to the man page
for icpc) are "Float-16 conversion instructions and the RDRND
instruction". Float16 conversion would fit the F16C acronym in the error 
message.

> Running short tests or compiled utilities on the head nodes is very
> convenient. I would continue to make sure the code runs everywhere until
> there is a proven performance benefit.
Yes, that is what I would do as well.

Yours,
Roland

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