Forum: Ruby Contest: fastet way to redefine a method

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Pit Capitain (Guest)
on 2006-12-27 18:01
(Received via mailing list)
Hi,

Dan Berger's recent thread about using UnboundMethod#bind to redefine an
existing method reminded me of a problem I still have:

   What is the fastest way to redefine an existing method?

With "fast" I don't mean the process of redefining the method, but the
time it takes to actually call the new implementation.

With "redefining an existing method" I mean changing the implementation
of an existing method so that in the new implementation it is possible
to call the old one and use its return value.

I've seen many different techniques in the past here on ruby-talk, but I
haven't looked at the tradeoffs. I promise to write a page on the ruby
garden wiki with the results.

Regards,
Pit
Trans (Guest)
on 2006-12-27 19:09
(Received via mailing list)
Pit Capitain wrote:
> With "redefining an existing method" I mean changing the implementation
> of an existing method so that in the new implementation it is possible
> to call the old one and use its return value.
>
> I've seen many different techniques in the past here on ruby-talk, but I
> haven't looked at the tradeoffs. I promise to write a page on the ruby
> garden wiki with the results.
>
> Regards,
> Pit

A cut is going to be just about the fastest I think since it is
essentially a subclass, although defining the "wrapping" method
requires a bit of additional overhead. Alias certainly has the least
overhead. I imagine before and after wraps as matz has suggested for
Ruby 2.0 would be faster, albiet they are more limited in capability
than cuts.

Keep in mind that every "wrap" will have a benchmark greater than the
orginal by neccessity b/c includes the originals call --so what's
really of interest is the difference from the original. Consdiering
that it is clear what the fastest way would be. To literally extract
the source code of the oringal method and wrap it via string
manipulation and eval the result as the new method. Of course, that's
not all that practical -- for starters I think you would need something
like ParseTree to even pull it off.

Anyway here's Ara's benchmarks with cuts/subclass added:

#
# Alias
#
class HashUsingAlias < Hash
    alias :old_hset :[]=

    def []=(key, value)
      self.old_hset(key, value)
    end
end

#
# Bind
#
class HashUsingBind < Hash
    hset = self.instance_method(:[]=)

    define_method(:[]=) do |key, value|
      hset.bind(self).call(key, value)
    end
end

#
# Override
#
require 'override'
class HashUsingOverride < Hash
   override('[]='){ def []=(k,v) super end }
end

#
# Subclass
#
class HashUsingSubClass < Hash
  def []=(k,v)
    super
  end
end

#
# Cut (pure ruby meta-hacking version)
#
require 'facets/more/cut'
class HashUsingCut < Hash; end

cut :HashUsingCutAspect < HashUsingCut do
  def []=(k,v); super; end
end

require "benchmark"
def bm_report bm, title, hash_class
   hash = hash_class.new
   bm.report title do
     100_000.times do
       hash[ 1 ] = 1
     end
   end
end

Benchmark.bmbm do |bm|
   bm_report bm, "original", Hash
   bm_report bm, "alias", HashUsingAlias
   bm_report bm, "bind", HashUsingBind
   bm_report bm, "override", HashUsingOverride
   bm_report bm, "subclass", HashUsingSubClass
   bm_report bm, "cut", HashUsingCut
end


Rehearsal --------------------------------------------
original   0.100000   0.020000   0.120000 (  0.125107)
alias      0.180000   0.030000   0.210000 (  0.226911)
bind       0.460000   0.050000   0.510000 (  0.525037)
override   0.590000   0.030000   0.620000 (  0.630301)
subclass   0.170000   0.030000   0.200000 (  0.210436)
cut        0.170000   0.030000   0.200000 (  0.210003)
----------------------------------- total: 1.860000sec

               user     system      total        real
original   0.100000   0.010000   0.110000 (  0.123498)
alias      0.170000   0.040000   0.210000 (  0.224580)
bind       0.480000   0.030000   0.510000 (  0.529366)
override   0.570000   0.050000   0.620000 (  0.626580)
subclass   0.170000   0.030000   0.200000 (  0.214458)
cut        0.170000   0.030000   0.200000 (  0.209727)
Robert Klemme (Guest)
on 2006-12-27 19:21
(Received via mailing list)
On 27.12.2006 17:59, Pit Capitain wrote:
>   What is the fastest way to redefine an existing method?
>
> With "fast" I don't mean the process of redefining the method, but the
> time it takes to actually call the new implementation.

So you mean runtime efficiency.

> With "redefining an existing method" I mean changing the implementation
> of an existing method so that in the new implementation it is possible
> to call the old one and use its return value.

I once cooked something together.  The code is on Ruby Garden:
http://wiki.rubygarden.org/Ruby/page/show/MethodHooks

No idea about performance etc.  At some point I stopped working on this
because it was said that Ruby 2 will include a feature for this.  I
remember that there were some limitations (i.e. no suppport for blocks
so far) but usability is ok IMHO.  This was mostly an experiment.

Kind regards

	robert
Eric Hodel (Guest)
on 2006-12-27 23:11
(Received via mailing list)
On Dec 27, 2006, at 08:59, Pit Capitain wrote:
> implementation it is possible to call the old one and use its
> return value.
>
> I've seen many different techniques in the past here on ruby-talk,
> but I haven't looked at the tradeoffs. I promise to write a page on
> the ruby garden wiki with the results.

I already did this:

http://blog.segment7.net/articles/2006/03/06/attr-...
define_method

You can probably match def for speed by using one of the eval methods.

--
Eric Hodel - drbrain@segment7.net - http://blog.segment7.net

I LIT YOUR GEM ON FIRE!
unknown (Guest)
on 2006-12-27 23:28
(Received via mailing list)
On Thu, 28 Dec 2006, Eric Hodel wrote:

> I already did this:
>
> http://blog.segment7.net/articles/2006/03/06/attr-...
>
> You can probably match def for speed by using one of the eval methods.

did you mean to say 'evil methods'  ;-)

-a
Eric Hodel (Guest)
on 2006-12-27 23:48
(Received via mailing list)
On Dec 27, 2006, at 14:26, ara.t.howard@noaa.gov wrote:
> did you mean to say 'evil methods'  ;-)
There's no need to use the evil eval:

$ parse_tree_show
class X; class_eval { def y() 5; end } end
[[:class,
   :X,
   [:const, :Object],
   [:defn, :y, [:scope, [:block, [:args], [:lit, 5]]]]]]

Which generates the same AST as a regular def:

$ parse_tree_show
class X; def y() 5; end; end
[[:class,
   :X,
   [:const, :Object],
   [:defn, :y, [:scope, [:block, [:args], [:lit, 5]]]]]]

If you use alias, the aliased method will be slightly slower:

$ parse_tree_show
class X; def y(); 5 end; alias x y; end
[[:class,
   :X,
   [:const, :Object],
   [:defn, :x, [:fbody, [:scope, [:block, [:args], [:lit, 5]]]]],
   [:defn, :y, [:scope, [:block, [:args], [:lit, 5]]]]]]

But you can use ruby2ruby to regenerate the aliased method without
the :fbody node (or, just inline it).  I'll leave this as an exercise
to the reader.

--
Eric Hodel - drbrain@segment7.net - http://blog.segment7.net

I LIT YOUR GEM ON FIRE!
unknown (Guest)
on 2006-12-28 00:12
(Received via mailing list)
On Thu, 28 Dec 2006, Eric Hodel wrote:

>> did you mean to say 'evil methods'  ;-)
>
> There's no need to use the evil eval:

sorry - just trying to be punny!

-a
Trans (Guest)
on 2006-12-28 01:36
(Received via mailing list)
On Dec 27, 5:09 pm, Eric Hodel <drbr...@segment7.net> wrote:
>
> http://blog.segment7.net/articles/2006/03/06/attr-...
> define_method

Post Not Found....
Eric Hodel (Guest)
on 2006-12-28 03:04
(Received via mailing list)
On Dec 27, 2006, at 16:35, Trans wrote:

>> http://blog.segment7.net/articles/2006/03/06/attr-...
>> define_method

Lies.

--
Eric Hodel - drbrain@segment7.net - http://blog.segment7.net

I LIT YOUR GEM ON FIRE!
Mat Schaffer (Guest)
on 2006-12-28 05:10
(Received via mailing list)
On Dec 27, 2006, at 7:35 PM, Trans wrote:
> On Dec 27, 5:09 pm, Eric Hodel <drbr...@segment7.net> wrote:
>>
>> http://blog.segment7.net/articles/2006/03/06/attr-...
>> define_method
>
> Post Not Found....

Looks like your mail reader is inserting hard line breaks.
-Mat
Trans (Guest)
on 2006-12-28 06:31
(Received via mailing list)
Mat Schaffer wrote:
> On Dec 27, 2006, at 7:35 PM, Trans wrote:
> > On Dec 27, 5:09 pm, Eric Hodel <drbr...@segment7.net> wrote:
> >>
> >> http://blog.segment7.net/articles/2006/03/06/attr-...
> >> define_method
> >
> > Post Not Found....
>
> Looks like your mail reader is inserting hard line breaks.

Interesting I'm using the google groups interface. I just noticed teh
address is split on Eric's post, but prefectly whole on Ara's. Strange.

T.
Pit Capitain (Guest)
on 2006-12-28 09:27
(Received via mailing list)
Eric Hodel schrieb:
> On Dec 27, 2006, at 08:59, Pit Capitain wrote:
>> I promise to write a page on the ruby garden wiki with the results.
>
> I already did this:
>
> http://blog.segment7.net/articles/2006/03/06/attr-...

Eric, thanks for the link. I'm sure these numbers will help, but they
are not exactly what I'm looking for. I'm looking for different
techniques to redefine a method in a way that still allows to call the
previous implementation. Personally, I'm mostly interested in fast
techniques, so your benchmark is very welcome.

Regards,
Pit
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