"somebody" <x### [at] ycom> wrote:
> "Kenneth" <kdw### [at] earthlinknet> wrote
>
> > BTW, in working with this technique (and running some other experiments),
> I've found that rand() doesn't actually HIT zero or one.
>
> A pseudo random generator should in practice not hit *any* given number, not
> just 0 and 1, unless you cover its period at least a few times. Further, in
> practice again, some (or many) numbers in range will simply be "unhittable".

Not sure I understand what you mean by *period*.  Would that be *all* the
possible numbers between 0 and 1 that can conceivably be found in Pov_Ray? In
one test I did--looking for a 0 or 1 hit --I used a #while loop that iterated
10,000,000 times. No "hits"--though, admittedly, that's not 2^32 tries. I
thought of actually going "to the limit," but demurred because of the quite
lengthy parse time involved. Is it possible that I just
haven't tried hard enough? So by the same reasoning: If I chose some value
between 0 and 1 at random--say, .0005674836--and actually TRIED to hit that
with rand(), would the possibility of success be the same as trying to hit 0 or
1--i.e., practically nil? I'm beginning to see some light here--that "0" and "1"
constitute just two of a huge range of possible hits...and I can't expect to
pick JUST those two exact values out of such an ocean of numbers--without
searching the entire ocean, so to speak (and multiple times!) BUT, I still
harbor the sneaking thought that 0 and 1 may *in fact* be out-of-range. Hard to
prove or disprove, I suppose. As a practical matter, they just don't ever
seem to pop up. But I suppose you could say the same thing about .0005674836!

Thanks for your comment; it has made me think about this situation in depth.

As to some values being unhittable--can't say I understand why, unless it has
something to do with underlying computational processes that I don't understand
(and I don't understand plenty, when it comes to such things! :-)

Ken W.

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