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Eric Mcintosh
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Message 41702 - Posted: 23 Feb 2020, 12:31:17 UTC

Dear All, thank you for your continued support.
I hope you had a Merry Christmas and I wish
you a Guid New Year.

I am back, but rather slow, after my recent heart operation.
My priority is to publish "IEEE 754 as intended - or how to
obtain identical double precision floating-point results".

SixTrack LHC@home is running well but tasks are
still being taken rather slowly and I reckon we use,
at best, one third of your provided capacity. Still your
support is vital for the High Luminescent LHC studies.

Personally I have a couple of issues:
I need to access old migrated data to define SixTrack
performance and this is a problem right now.
While the Invalid result error rate is in general very low,
24 Invalid and over one million valid today, I need to
identify the genuine computational errors.

You can find my recent CERN Open Days presentation at along with the state
of my research. Eric
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Message 41703 - Posted: 23 Feb 2020, 13:07:13 UTC - in response to Message 41702.  

Dear Eric,

Happy to see you are still able to work on that.
Best regards.
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Message 41708 - Posted: 23 Feb 2020, 21:36:10 UTC

Hello Eric,

I was about to email you but just happened to check here first and good to see you here again.

Maybe I will send you an email anyway.

And have been running all the Sixtracks I can get here lately but it tends to be like 2004 except I have many more cores to use these days.
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Message 41712 - Posted: 24 Feb 2020, 9:18:27 UTC - in response to Message 41702.  

Double precision maths is luckily the modern CPU core FPU feature..
Precision of 2 errors over 1000000 result will mean one or two errors per trillion calculations,
However feasible perfectly error free results are..
The net result is believably within the error factor posed by Intel guidelines.

Error free incites perfect pre-fetch and super class stability,
The facts remain the same on error count:

AVX float buffer overrun,
FPU Buffer overrun.
Rounded results.

Most plausibly a buffer over run.
Consistently very high precision numbers require a 180 bit buffer...
Around 16KB stack buffer should prevent overflow (per result)
Compressing the resultant into a compressed memory zip saves data space.

perhaps this will help:
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Message boards : Cafe LHC : Status 2020

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