<div dir="ltr">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.<div><br></div><div>To my knowledge, the processors accept the same machine instructions. The CPU tuning might be different.</div><div><br></div><div>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.</div><div><br></div><div>-erik</div><div><br></div></div><div class="gmail_extra"><br><div class="gmail_quote">On Sun, Sep 18, 2016 at 2:36 PM, Roland Haas <span dir="ltr"><<a href="mailto:rhaas@illinois.edu" target="_blank">rhaas@illinois.edu</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Hello all,<br>
<br>
NERSC's edison cluster specifies -xHost in its cfg file. However login<br>
nodes and compute nodes are actually different (Sandy Bridge vs. Ivy<br>
Bridge cpus).<br>
<br>
A quick test removing -xHost reveals a possible reason: without -xHost<br>
the compiled exectuables do not run on the head node. No for the actual<br>
question: is it worthwhile to claim cross compilation (and the<br>
requirement to have to specify endianess, type sizes etc manually) to<br>
possibly gain some more speed?<br>
<br>
Given that Ivy and Sandy Bridge are tick and tock I would not expect<br>
much of a gain (though maybe Ivy Bridge actually offers wider AVX<br>
instructions?).<br>
<br>
At least I will add a comment to edison.cfg explaining why either<br>
-xHost is used or why a cross compilation is required.<br>
<br>
Yours,<br>
Roland<br>
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<br></blockquote></div><br><br clear="all"><div><br></div>-- <br><div class="gmail_signature" data-smartmail="gmail_signature">Erik Schnetter <<a href="mailto:schnetter@cct.lsu.edu" target="_blank">schnetter@cct.lsu.edu</a>><br><a href="http://www.perimeterinstitute.ca/personal/eschnetter/" target="_blank">http://www.perimeterinstitute.ca/personal/eschnetter/</a></div>
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