Message boards : Number crunching : I found an Anomaly
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Profile Steve Cressman
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Message 15958 - Posted: 2 Jan 2007, 2:55:46 UTC
Last modified: 2 Jan 2007, 2:58:49 UTC

Was just looking through my results for this run and found something that needs to be checked out. It was not my client with the problem, but I thought it best to point it out. THis work unit is the one I'm refering to. The 4th one in, computer # 159657, has recieved only half the points of the 3 of us who made up the quorum. Never saw this happen before. If you look at the result Details it was marked invalid. Should it not then receive zero for this result?

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Message 15959 - Posted: 2 Jan 2007, 6:28:49 UTC - in response to Message 15958.  

Was just looking through my results for this run and found something that needs to be checked out. It was not my client with the problem, but I thought it best to point it out. THis work unit is the one I'm refering to. The 4th one in, computer # 159657, has recieved only half the points of the 3 of us who made up the quorum. Never saw this happen before. If you look at the result Details it was marked invalid. Should it not then receive zero for this result?

Steve


Interesting. But I think it's ok. The client reported data not knowing that it's false. The server compared the other results and found propably some mistake and marked it invalid. Still, the client had reported data and therefore is granted some credit. Three valid results have been found. I think it is fair that although that specific WU had one invalid result, still everyone does get some credit.
Haven't seen that before.

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Message 15961 - Posted: 2 Jan 2007, 10:12:47 UTC

What's worrying is that all the recent results of that comp were deemed invalid by the validator. And got about 50% credits granted anyway. Maybe CC 5.8.0 has something to do with this?
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Profile Steve Cressman
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Message 15963 - Posted: 2 Jan 2007, 12:42:58 UTC - in response to Message 15961.  
Last modified: 2 Jan 2007, 12:45:29 UTC

What's worrying is that all the recent results of that comp were deemed invalid by the validator. And got about 50% credits granted anyway. Maybe CC 5.8.0 has something to do with this?


I doubt that is the problem since I'm also using v5.8.0 without problems.
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Message 15967 - Posted: 2 Jan 2007, 19:42:07 UTC
Last modified: 2 Jan 2007, 19:42:57 UTC

ive been noticing the same problem on some of my work units. two of my computers have WU that only received half of the credits that others have received.

http://lhcathome.cern.ch/workunit.php?wuid=1578620

Im not too worried though, for some WUs I received 3X what I claimed so I guess it all balances out in the end


that said i don't really want to hand in invalid units, kind of a waste of time. Can anyone suggest a way to prevent my computer from crunching invaild units?
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Message 15969 - Posted: 2 Jan 2007, 21:21:13 UTC - in response to Message 15961.  

What's worrying is that all the recent results of that comp were deemed invalid by the validator. And got about 50% credits granted anyway. Maybe CC 5.8.0 has something to do with this?

This project has been granting half credit for results that are close for a long time. They have very tight validation requirements so more results fail validation than at most projects. The half credits even this out somewhat.
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Message 15972 - Posted: 2 Jan 2007, 22:03:17 UTC

NOW -- That is something I did not know.

My thanks to Keck Komputers for that tidbit of information ...


If I've lived this long, I've gotta be that old
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Profile Steve Cressman
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Message 15973 - Posted: 2 Jan 2007, 22:33:04 UTC

I've been here over two years and didn't know that and have never seen it in the results before the one I pointed out.
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Message 15974 - Posted: 2 Jan 2007, 23:24:16 UTC - in response to Message 15973.  

I've been here over two years and didn't know that and have never seen it in the results before the one I pointed out.


Hey Steve,
Maybe your have forgotten about this thread which caused quite a stir at the time :). Warning - it's quite a long thread with a bit of aggro at times but good for a laugh at how passionate some people become about credit.

If you just want the definitive answer about half credits, check out this post in that thread by Markku Degerholm who was one of the admins at the time, I think. My impression was that he entered the fray in an attempt to hose things down. He was pretty successful as the thread (which had been running for over a month) died soon after he made a couple of posts.

As far as not seeing half credits in the results, I guess it depends on how much you stress your computers. I like to overclock moderately and I've found that LHC WUs are the most sensitive indicator of the first tiny instability if you push it a little bit too far. I've had machines that are rock solid on other projects which give an occasional half credit result on LHC. If I backoff the overclock just a fraction, the problem usually disappears. I think it's a very useful feature for judging machine stability.

Cheers,
Gary.
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Message 15976 - Posted: 3 Jan 2007, 3:19:41 UTC

The main reason that the 'half credits' came about was because there's a slight difference between the AMD and Intel Floating point results when performing certain math functions. Mutiply a bit error over a million loops of the simulation, and you can get two sets of 'correct' results based on which cpu you get.

Either way, Intel or AMD, they know that the particle had a stable orbit over a million cycles.
I'm not the LHC Alex. Just a number cruncher like everyone else here.
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Profile Steve Cressman
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Message 15978 - Posted: 3 Jan 2007, 5:14:03 UTC

Wow, thanks Gary. And I too like to push my system. Stock speed for this one is 1.8 GHz but I'm running rock solid stable at 2.1 GHz . Been running at that speed for close to 3.5 years but ran it at stock speed for couple weeks first to break it in. With some chip coolers I could go higher but never seem to get around to picking some up.

:) Steve
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Message boards : Number crunching : I found an Anomaly


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