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Old 2006-04-26, 03:05   #1
PhilF's Avatar
Feb 2005

10000010112 Posts
Default Unusual error - comments George?

I received a SUM(INPUTS) != SUM(OUTPUTS) error.

The unusual part is that a got a "Disregard last error. Result is reproducible and thus not a hardware problem." I thought reproducible errors only happened on round off errors when testing an exponent near the FFT size limit. This exponent (34685927) is not near an upper FFT boundary limit.

Thoughts? Has anyone ever had a SUM(INPUTS) != SUM(OUTPUTS) error that was reproducible?

Additional info: The two sums are very close:

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Old 2006-04-26, 17:34   #2
axn's Avatar
Jun 2003

22×11×107 Posts

Assuming that you are using a P4, did it use the 1792K FFT or 2048K FFT? I am guessing that it is the former which would explain the error.

Just a SWAG
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Old 2006-04-26, 20:19   #3
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Aug 2002
Yeehaw, FL

7·1,019 Posts

This "error" can happen with any FFT size, any exponent. It is an error check that compares two floating point values for "equality". Since it is impossible to compare floats for exactly, it makes sure the difference is "small". Small is computed based on some historical data and adjusted so that false error reports will be rare.

It looks like you just had an iteration where the difference was several standard deviations greater than normal.
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