Mailing List Archive: 49091 messages

# Two implementations...

### [1/5] from: rgombert::essentiel::net at: 5-Feb-2003 18:24

Hi all rebolers, I'm back to rebol after two year, and have great times playing with it ;-) I wanted to show some optimisation possible for some recursive computation, and wrote the small program below. Run the test, it talks for itself... I know this is nothing new for most of you... but maybe it can be of some help for someone ;-) Have fun with it... ############### CODE ############### REBOL [ title: "Test for two implementation of FIBONACCI function" author: "Renaud GOMBERT" notes: { slowfib use the intuitive way of implementing fib(n). fastfib do the same, but use a block to store allready known values of fibo(n). * As fastfib store all results, it is provided with a refinement to release them. * Both functions works for positive integers. * Max calculable value is fib(46), according to Rebol math capabilities. * If you want to waste CPU time, try running slowfib 46 LOL ;-) } ] krono: func [code n /local T][ prin [code "running" n "times... "] T: now/time/precise print ["and return:" loop n [do code] ", taking:" (now/time/precise - T)] ] slowfib: func [n][ either n < 2 [n][add slowfib n - 2 slowfib n - 1] ] fastfib: function [n /release][r][ accu: [1 1] r: either n <= length? accu [ accu/:n ][ last append accu add fastfib n - 2 fastfib n - 1 ] if release [clear at accu 3] r ] ; TEST RUN do [ print "TESTING THE TWO FIB FUNCTIONS :^/" krono [slowfib 25] 10 krono [fastfib 25]10 krono [fastfib/release 25]10 krono [slowfib 30] 5 krono [fastfib 30] 5 krono [fastfib/release 30] 5 krono [fastfib 46] 10000 krono [fastfib/release 46] 10000 krono [fastfib 46] 1450000 krono [slowfib 11] 10000 ] halt ############### END OF CODE ############### --------------------- Renaud GOMBERT - www.essentiel.net

### [2/5] from: greggirwin:mindspring at: 5-Feb-2003 11:38

Thanks Renaud! Good stuff, and if you put the function in a context with ACCU as a word in the context, you can avoid it being a global word. -- Gregg

### [3/5] from: joel:neely:fedex at: 5-Feb-2003 13:54

Hi, Gregg and Renaud, Gregg Irwin wrote:
> Good stuff, and if you put the function in a context with ACCU as a > word in the context, you can avoid it being a global word. >
It's not necessary to use an object. Simply define ACCU as /LOCAL and let the persistence of literal values take care of the rest. That way ACCU isn't global either. -jn- -- ---------------------------------------------------------------------- Joel Neely joelDOTneelyATfedexDOTcom 901-263-4446 Atlanta, Ga. - Scientists at the Centers for Disease Control today confirmed that hoof-and-mouth disease cannot be spread by Microsoft's Outlook email application, believed to be the first time the program has ever failed to propagate a major virus.

### [4/5] from: rgombert:essentiel at: 5-Feb-2003 21:10

From: "Gregg Irwin" <[greggirwin--mindspring--com]
>> Thanks Renaud! > Good stuff, and if you put the function in a context with ACCU as a > word in the context, you can avoid it being a global word.
Yes, it's a way ;-) In fact i just forgotten to include 'ACCU in the local variable definition block : fastfib: function [n /release][r accu][ function_body ] Just for those who haven't tried the script : * slowfib 35 : need about 49 seconds to return on my PC * fastfib/release 35 : can be run 170000 times winthin 49 seconds * fastfib 35 (not releasing each time) run 170000 times in 0.4 s -------------------------------- Renaud GOMBERT - www.essentiel.net

### [5/5] from: greggirwin:mindspring at: 5-Feb-2003 14:08

Hi Joel, JN> It's not necessary to use an object. Simply define ACCU as /LOCAL and JN> let the persistence of literal values take care of the rest. That JN> way ACCU isn't global either. DOH! Of course, he's not COPYing the initial block. Thanks for catching me. -- Gregg