From: "Jonas Pfenniger (zimbatm)" <jonas@...>
Date: 2011-01-13T21:39:01+09:00
Subject: Re: Why {} is much faster than Hash.new ?

I think it's the cost of the method call with options parsing.

Benchmark.realtime do 1_000_000.times do @m = Hash.new end end
 => 1.1976041793823242

def blank_method; end
Benchmark.realtime do 1_000_000.times do @m = blank_method end end
 => 0.1965808868408203

Benchmark.realtime do 1_000_000.times do @m = {} end end
 => 0.2893531322479248

Benchmark.realtime do 1_000_000.times do @m = Hash.allocate end end
 => 0.3925323486328125

You see that Hash.allocate's time is about the same as ({} +
blank_method). The rest comes from option parsing I guess.

2011/1/13 Iñaki Baz Castillo <ibc@aliax.net>:
> Hi, a simple benchmark:
>
> Benchmark.realtime { 1000000.times { @m = Hash.new } }
> => 0.6552023887634277
>
> Benchmark.realtime { 1000000.times { @m = {} } }
> => 0.17668819427490234
>
> I would like to know why {} is so much faster. I can understand that
> Hash.initialize method must inspect is an argument is given and so, is
> just due to it?
>
> Thanks.
>
>
> --
> Iñaki Baz Castillo
> <ibc@aliax.net>
>
>