From: Chet Nichols III <chet.nichols@...>
Date: 2007-11-14T12:49:15+09:00
Subject: efficiency of recursion (stack level too deep)

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hi there-

so i started running into a problem using recursion with ruby- it seemed a
little too soon for me to be getting a stack overflow ('stack level too deep
(SystemStackError)'), so i wrote up a quick simple script to do some
recursion:

-----
#!/usr/local/bin/ruby

def print_depth num
 puts num
 print_depth(num+1)
end

print_depth 0
-----

and sure enough, once im at a recursive depth of about 4,360, it errors out.
i tried making num a global $num instead so it wasnt allocating memory on
the stack each time for building a new 'num' object, but that only got me to
about 4,500 until the overflow. to me, it seems a little low, especially for
something this simple. my stack size is 10240. and, of course, when i up it
to something like 20480, i get about double the recursive depth.. but when i
try the same thing in C:

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#include <stdio.h>

void print_depth(int num);

int main() {
    print_depth(0);
}

void print_depth(int num) {
    printf("%d\n",num);
    print_depth(++num);
}
-----

i get a recursive depth of about 350,000 before it bombs out (which is what
i'd expect more or less). i know C is super efficient and all, and ruby is
truly object oriented, so each thing pushed on the stack is an object with
its own set of methods, etc, so its by design going to take up more space,
but i was wondering if there are any plans to do anything to help the
efficiency of this at all?

to be honest, i've only been using ruby for about a week now, and i totally
love it. so, this e-mail really isn't a complaint at all, just more of a
question. if there's already an answer (which there probably is), feel free
to shout it out- i love everything i've seen and done so far with the
language, so the more i know about it, the better! hope to hear from someone
soon- thanks!

chet

-- 
/*
Chet Nichols III
call: 703.310.9174
mail: chet.nichols@gmail.com
aim: chet
*/

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