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Re: Recursion: An example of Looping and Recursion

by lolindrath (Scribe)
on Nov 16, 2000 at 07:15 UTC ( #41936=note: print w/ replies, xml ) Need Help??


in reply to Recursion

This is the Euclidean algorithm for finding the Greatest common divisor between two numbers. I thought I'd throw a bit of my own code into the fray. The first one uses a loop, the second uses recursion. Could someone benchmark this for me?

#!/usr/bin/perl -w print "GCD: " . GCD( 45, 5 ) . " RecGCD: " . RecGCD( 45, 5 ) . "\n"; #Assumes $A is the largest number sub GCD { $A = shift; $B = shift; $R = 1; while ( $R != 0 ) { $R = $A % $B; if ( $R == 0 ) { return $B; } $A = $B; $B = $R; } } #Assumes $A is the largest number sub RecGCD { $A = shift; $B = shift; $R = 0; $R = $A % $B; if ( $R == 0 ) { return $B; } RecGCD( $B, $R ); }


--=Lolindrath=--


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Re: Re: Recursion: An example of Looping and Recursion
by extremely (Priest) on Nov 16, 2000 at 11:08 UTC
    Whoop! a benchmark question! Ahhh...
    # for 45, 5
             Rate  loop recur
    loop  30118/s    --  -37%
    recur 47528/s   58%    --
    
    # for 296, 111
             Rate recur  loop
    recur  9303/s    --  -36%
    loop  14426/s   55%    --
    
    # for 298, 111
            Rate recur  loop
    recur 4672/s    --  -45%
    loop  8445/s   81%    --

    Interesting what a win the loop version is on that last one...

    --
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    honk() if $you->love(perl)

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