From: Ryan Davis <ryand-ruby@...>
Date: 2007-10-04T05:19:22+09:00
Subject: Re: hash key performance


On Oct 2, 2007, at 23:46 , Matthias W��chter wrote:

> On 02.10.2007 16:55, Marcin Miel��y��ski wrote:
>> Matthias W��chter wrote:
>>
>>> But here it comes: Using false and, even worse, nil (in either
>>> literal or variable form) is way slower (a good 20%) than using
>>> integers and symbols, even if they follow the same "immutable
>>> object" philosophy of fixed object_ids.
>>>
>>> Why is that? What's so special about false and nil to have such a
>>> degraded performance as a hash key?
>>>
>>
>> hash.c:rb_any_hash is the answer to your question (funcall('hash') is
>> discarded only for Fixnums, Symbols and Strings.
>
> So the first two cases of "switch (TYPE(a))" should be enhanced with
> checks for nil, true and false like this:
>
>     switch (TYPE(a)) {
>       case T_FIXNUM:
>       case T_SYMBOL:
> +     case T_NIL:
> +     case T_FALSE:
> +     case T_TRUE:
> 	return (int)a;
> 	break;

Send that and your original timings to ruby-core@ and/or file a bug  
on rubyforge in the ruby project.