"Warp" <war### [at] tagpovrayorg> wrote in message 
news:486340c6@news.povray.org...
>  Unrelated to this topic in particular, but related to rounding. There's
> a curious anecdote about rounding in FPUs:
>
> ... most FPUs simply clamp those bits away, period, without
> any kind of rounding.
> ...
>  In some FPU ... they ... round the value up or down *randomly*.... the 
> rounding
> errors caused by the regular clamping method were significant, the random
> method caused much smaller rounding errors.
> ...
> Assuming that approximately half of the results
> would indeed have to be rounded down and the rest up, the random rounding
> produces, with lengthy calculations, a result which is much closer to the
> correct one.

But a result which is not necessarily the same each time you calculate the 
answer using the same dataset as input.

Regard,
Chris B.

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