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[REBOL] Re: Fibonaccio - Was: Report on WinCE Rebol --- Speed Comparison

From: bard:papegaaij:austarnet:au at: 29-Jun-2001 15:59

David Ness wrote:
>Bard Papegaaij wrote: >> >> Hi, >> >> I noticed you are using a recursive fibonaccio function to measure speed
>> different platforms. Some time ago I implemented a fibonaccio generator
as a
>> way of learning various aspects of REBOL. Features I used are: >> - an object to store the function and some house-keeping variables; >> - an iterating definition instead of the recursive one to get rid of
>> overflows; >[snip] >... > >If one were actually interested in generating fibonacci numbers then
>recursion nor iteration nor memory functions are needed as there is, IIRC, >a straightforward closed form for the fibonnaci which would evaluate for >any N at the cost of a couple of logs and a couple of exponentials.
Mmmmm. I didn't know about that one? Any pointers I could follow up? As far as I know, the fibanoccio series approximates - but never quite reaches - a true logarithmic progression. A solution using logs and exponentials sounds interesting.
>The objective here was, of course, to compare the machines and thus we
>to use functions that consumed some detectable amount of time. Trying to >make those functions `efficient' doesn't, it is clear, make sense for that >purpose.
I understand completely. It was just that I saw you using the fib function, and thought it would be nice to share my attempts at coding the same function using a number of different 'solutions' for some of the problems posed by that simple recursive definition (speed, inability to calculate higher than fib 42, stack overflow). Sorry if I have thrown you off track by 'hi-jacking' your thread for something like this. It won't happen again I ('m not sure I can) promise ;-). Regards, Bard