Thread: Suspect results
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Old 2018-02-17, 00:06   #8
ATH's Avatar
Dec 2003

3,037 Posts

You can add these values to prime.txt to help near the FFT boundaries..

From undoc.txt:

The program no longer uses hard FFT crossover points. The soft crossovers
have two adjustments in prime.txt:
The first setting controls which exponents are examined. The default value
is 0.2. This means that an exponent that is 0.2% above or below an FFT
crossover point are tested for the best FFT size to use. A value of 0.0
will turn off this soft FFT crossovers feature. The second setting
defaults to 0.000. This controls how aggressive or conservative the program
is in selecting the best FFT size. The program normally uses the smaller
FFT size if the average roundoff error is below a value in 0.241 to 0.243
range. If you set SoftCrossoverAdjust to say 0.003 then the program will
use the smaller FFT size if the average roundoff error is below a value
in 0.244 to 0.246 range. This will generate more iterations that generate
roundoff error above 0.40 warnings and a time loss returning to the previous
save file. It also increases the chance that a deadly roundoff error
above 0.6 will occur. On the plus side, using the smaller FFT size each
iteration will be a bit quicker. I wouldn't set this adjustment to more
than 0.006. If you set SoftCrossoverAdjust to say -0.002, then the program
will be more conservative and use the larger FFT size more often.
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