From: Joe Van Dyk <joevandyk@...>
Date: 2005-08-16T03:00:51+09:00
Subject: Re: no clue

On 8/14/05, Ara.T.Howard <Ara.T.Howard@noaa.gov> wrote:
> On Sun, 14 Aug 2005, Joe Van Dyk wrote:
> 
> >> On Sun, 14 Aug 2005, Joe Van Dyk wrote:
> <snip>
> > Thanks!  I shall study this code (there's a few new idioms that I
> > haven't used before) and report back early next week on the
> > performance improvements.
> 
> try this one - it's another order of magnitude faster:
> 
> 
>      harp:~ > ruby a.rb
>      #<PlayerData:0xb75cc0b4 @to_s=nil, @data=[400, 1.0, 2.0, 3.0, 42], @to_bin=nil>
>      400
>      1.0
>      42
>      pid : 400, x_position : 1.0, y_position : 2.0, z_position : 3.0, foobar : 42
>      creations per second : 114797
> 
> 
>      harp:~ > cat a.rb
>      class PlayerData
>        class << self
>          def create(*a)
>            new(a.pack(FORMAT))
>          end
>        end
> 
>        SPEC = [
>          %w( pid        i ),
>          %w( x_position f ),
>          %w( y_position f ),
>          %w( z_position f ),
>          %w( foobar     i ),
>        ]
> 
>        ATTRIBUTES = SPEC.map{|s| s.first}
> 
>        FORMAT = SPEC.map{|s| s.last}.join
> 
>        SPEC.each_with_index do |spec, ix|
>          at, format = spec
>          eval <<-src
>            def #{ at }
>              @#{ at } ||= @data[#{ ix }]
>            end
>            def #{ at }= value
>              raise TypeError unless self.#{ at }.class == value.class
>              uncache
>              @#{ at } = @data[#{ ix }] = value
>            end
>          src
>        end
> 
>        def update buffer
>          uncache
>          @data = buffer.unpack FORMAT
>        end
>        alias initialize update
>        def uncache
>          @to_s = @to_bin = nil
>        end
>        def to_s
>          @to_s ||= ATTRIBUTES.inject(''){|s,a| s << "#{ a } : #{ send a }, " }.chop.chop
>        end
>        def to_bin
>          @to_bin ||= @data.pack(FORMAT)
>        end
>      end
> 
>      id, x_position, y_position, z_position, foobar =
>        400, 1.0, 2.0, 3.0, 0b101010
> 
>      pd = PlayerData::create id, x_position, y_position, z_position, foobar
> 
>      p pd
>      p pd.pid
>      p pd.x_position
>      p pd.foobar
>      puts pd
> 
>      begin
>        require 'timeout'
>        n = 0
>        sec = 10
>        Timeout::timeout(sec) do
>          loop do
>            PlayerData::create id, x_position, y_position, z_position, foobar
>            n += 1
>          end
>        end
>      rescue Timeout::Error
>        puts "creations per second : #{ n / sec }"
>      end
> 
> 
> basically it just unpacks everything and then uses lazy evaluation to get the
> values when asked.  it's hard to imagine getting faster than this, but someone
> will surely prove me wrong ;-)

So, say I want to use a class similar to this called
'ApplicationData'.  The only changes would be the SPEC.

Would the 'ruby way' be to have a base class (say, 'Data'), and then
have PlayerData and ApplicationData inherit from Data and have them
override the SPEC?

Thanks,
Joe