Message boards : Number crunching : which CPU extension in use for which sub-projects?
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Erich56

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Message 33938 - Posted: 19 Jan 2018, 15:11:11 UTC

the recent introduction of use of AVX code for some Sixtrack WUs leads me to the question as to whether Sixtrack would now be the only LHC subproject making use of AVX (besides SSE2), or whether the other subprojects, running as VM, are already using AVX. If not, any idea which extensions (maybe newer ones than SSE2) are being used for the various projects?
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Erich56

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Message 34065 - Posted: 24 Jan 2018, 14:52:13 UTC - in response to Message 33938.  

none of the mods or anyone else any idea?
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computezrmle
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Message 34079 - Posted: 25 Jan 2018, 7:29:30 UTC - in response to Message 33938.  

the recent introduction of use of AVX code for some Sixtrack WUs leads me to the question as to whether Sixtrack would now be the only LHC subproject making use of AVX (besides SSE2), or whether the other subprojects, running as VM, are already using AVX. If not, any idea which extensions (maybe newer ones than SSE2) are being used for the various projects?

I'm not quite sure what you expect.

1. An AVX version of the vbox wrappers?
2. AVX versions of the scientific apps inside the VMs?


(1)
Makes no sense as there are not much floating point calculations to be done by the wrappers.

(2)
Could make sense under certain prerequisits but those apps would be integrated in the downloads at the beginning of a job.
Perhaps your VMs already use AVX apps.

Cheers
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ivan
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Message 34083 - Posted: 25 Jan 2018, 11:45:29 UTC - in response to Message 34079.  

As far as I know, CMS software does use AVX, because when we benchmarked our stuff on a Knight's Landing cluster it was stated that we might have got better performance if we'd recompiled to make use of its AVX512 instructions instead of the AVX256 default. At that time no standard CPU had AVX512, but that has now changed of course.
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Message boards : Number crunching : which CPU extension in use for which sub-projects?


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