From: "Bartosz Dziewoński" <matma.rex@...>
Date: 2012-03-25T03:26:47+09:00
Subject: Re: Ruby speed compared to C in a simple calculations.

W dniu 24 marca 2012 18:55 użytkownik Josh Cheek <josh.cheek@gmail.com> napisał:
> Numbers are actual objects that must be allocated, for example.

Fun fact: it's thankfully not *that* bad. Numbers up to 2**30-1 are
not actually allocated; instead, they're magically stored in the C
pointer which would normally point at the location of associated
object. Symbols are handled similarly (that's why you should always
use them instead of strings when the actual string values does not
matter).

See for yourself. For regular objects, #object_id returns numerical
values of location in memory where it is stored (that is, values of C
pointer to this object). But...

irb(main):001:0> 1.object_id
=> 3
irb(main):003:0> 100.object_id
=> 201
irb(main):005:0> 120.object_id
=> 241
irb(main):007:0> 200.object_id
=> 401

Here you see a pattern: small numbers' object_id are equal to the
number, doubled, plus one.

irb(main):015:0> 2**30-1
=> 1073741823
irb(main):016:0> (2**30-1).object_id
=> 2147483647
irb(main):017:0> (2**30-1).class
=> Fixnum

The pattern still holds.

irb(main):018:0> 2**30
=> 1073741824
irb(main):019:0> (2**30).object_id
=> 6594348
irb(main):020:0> (2**30).class
=> Bignum

No more! Our number was promoted to a Bignum, which is actually
allocated separately - the object_id value is no longer magical, it's
just a straight pointer to a location in memory. (It will be different
on your machine.)

-- Matma Rex