From: Louis Krupp <lkrupp@...>
Date: 2003-01-12T11:47:49+09:00
Subject: Re: Ruby:  politics & performance [long]

Phil Tomson wrote:

> In article <200301111701.12221.transami@transami.net>,
> Tom Sawyer  <transami@transami.net> wrote:
<snip> 
>>one option might be to use hashes in place of arrays. you can index them 
>>yourself. instead of [a, b, c] use {0=>a, 1=>b, 2=>c}. hashes, i was suprised 
>>to discover, are around 12x faster than arrays.
> 
> except that he's talking about list_append as used in the parser... I 
> don't think using hashes will help at all.  It seems that the issue has to 
> do with node lists which are constructed by the parser.

Correct -- I think it's this bit of parse.y:

---
args 		: arg
		    {
			value_expr($1);
			$$ = NEW_LIST($1);
		    }
		| args ',' arg
		    {
			value_expr($3);
			$$ = list_append($1, $3);
		    }
		;
---

For the first item in the list, list_append has to check one
node, for the second it looks at two, and
1 + 2 + 3 + ... + n = (n**2 + n)/2 traversals for n items.

list_concat does basically the same thing.

Meanwhile, I'm learning some things about Ruby.  NArray will almost
certainly be better than using generic arrays for lists of what I
know will be numbers.

Another poster suggested DATA.read.split, and that would work if I
had only one array to worry about.  Unfortunately, there are a
bunch of them, and they're scattered throughout the generated
script.

Thanks to everyone for the replies!

Louis