On Sun, Sep 18, 2016 at 4:24 PM, Roland Haas <rh...@illinois.edu> wrote:
> Hello Erik,
> > It's strange that code without "-xHost" does not run on the head node.
> > 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:
> Please verify that both the operating system and the processor support
> Intel(R) F16C instructions.
> 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
The best option for us is then probably "-xHost -axCORE-AVX-I". This
ensures (-x) that the code runs on the front end, but it will apply code
optimizations (-ax) for the compute nodes.
Erik Schnetter <schnet...@cct.lsu.edu>
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