Steinar found:

> and the following by George Woltman:
> 
> | Now the gotcha.  In v22.8, FFT crossovers are flexible.  If you test an
> | exponent within 0.2% of a crossover point, then 1000 sample iterations
> | are performed using the smaller FFT size and the average roundoff
> | error calculated.  If the average is less than 0.241 for a 256K FFT or
> | 0.243 for a 4M FFT, then the smaller FFT size is used.

Could someone (Brian?:))) sketch a histogram showing how the rounding
errors from -0.5 to +0.5 are dstributed in the above case please.
I am bemused ATM. There seems to be something spooky about these things.

At least the "0.2%" is "evidence" for the sharpness of the crossover point, 
Steinar.

David


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