Message boards : Number crunching : Modern computers behave in wildly unpredictable ways ...
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Message 22040 - Posted: 11 Mar 2010, 2:41:52 UTC

and what are the consequences for BOINC projects ?
Just read:
http://www.physorg.com/news187463445.html

\\\"If you enter the same computer command, you should get back the same result. Unfortunately, that is far from the case with many of today\\\'s machines. Beneath their smooth exteriors, modern computers behave in wildly unpredictable ways, said Luis Ceze, a UW assistant professor of computer science and engineering.

\\\"With older, single-processor systems, computers behave exactly the same way as long as you give the same commands. Today\\\'s computers are non-deterministic. Even if you give the same set of commands, you might get a different result,\\\" Ceze said.

He and UW associate professors of computer science and engineering Mark Oskin and Dan Grossman and UW graduate students Owen Anderson, Tom Bergan, Joseph Devietti, Brandon Lucia and Nick Hunt have developed a way to get modern, multiple-processor computers to behave in predictable ways, by automatically parceling sets of commands and assigning them to specific places. Sets of commands get calculated simultaneously, so the well-behaved program still runs faster than it would on a single processor.\\\"
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Message 22043 - Posted: 11 Mar 2010, 10:27:11 UTC - in response to Message 22040.  

For BOINC? I don\'t know. For LHC@home? Probably nothing. bigmac is using libraries and methods so that all computers will give back identical results even down to 15 decimal places or more. I can\'t find the paper at the moment but he just gave a seminar here at QMUL about it.
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Message 22050 - Posted: 11 Mar 2010, 15:01:08 UTC

They just say it\'s non-deterministic and they are right with that, but I can\'t see the problem why a cpu should deliver wrong results.
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Message boards : Number crunching : Modern computers behave in wildly unpredictable ways ...


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