Re: Performance of Recursion vs Iteration in PicoLisp

[Alexander Burger]

Hi Thorsten,

> since I just wrote a little Wiki article about recursion in PicoLisp, I
> would be curious about how recursion performs in comparison to iteration
> in PicoLisp.

OK, let's try. If I run this:

   # Recursive
   (bench
      (do 1000000
         (let (N 100)
            (recur (N)
               (if (=0 N)
                  1
                  (* N (recurse (dec N))) ) ) ) ) )

   # Iterative
   (bench 
      (do 1000000
         (let N 1
            (for I 100
               (setq N (* I N)) )
            N ) ) )

   # Simple
   (bench 
      (do 1000000
         (apply * (range 1 100)) ) )

then I get:

   13.161 sec
   7.331 sec
   7.413 sec
   -> 
93326215443944152681699238856266700490715968264381621468592963895217599993229915608941463976156518286253697920827223758251185210916864000000000000000000000000

So the recursive version takes about twice as long as the other two.


> The notion of 'tail-recursion' does not have any meaning in an
> interpreted language like PicoLisp, since its only for compiler
> optimizations -right?

Yes.

♪♫ Alex
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