From: Alexandru Popescu <the.mindstorm.mailinglist@...>
Date: 2006-07-01T10:00:12+09:00
Subject: Re: Is a block converted to a Proc object before yield?

While to anybody else this code made things clear, for me it is still
a little bit confusing:

why outer12 is performing slower than outer22?

According to prev posts, I have understood that the usage of
block.call requires a conversion to a Proc and this is slower. But in
above case where is this conversion taking place? (or simply, why is
it slower?).

thanks (and sorry to be confused),

./alex
--
.w( the_mindstorm )p.
---
(http://themindstorms.blogspot.com)


On 6/29/06, Joel VanderWerf <vjoel@path.berkeley.edu> wrote:
> Sam Kong wrote:
> > Hello!
> >
> > As you know, in Ruby, a block is not an object for some reasons, one of
> > which is performance.
> >
> > def f
> >   yield
> > end
> >
> > def g &blk
> >   blk.call
> > end
> >
> > In g, a block is explicitly converted to a Proc object.
> > What about in f?
> > Is a block still converted to a Proc object implicitly?
> >
> > If it's not converted, I understand the performance issue.
> > However, it's always converted to a Proc object, I don't understand why
> > blocks improve performance just because they are not objects.
> >
> > Can somebody explain this, please?
>
> You've got the answer already, but it's interesting to see how much of a
> difference it makes: (YMMV, of course.)
>
> require 'benchmark'
>
> def outer11(&bl)
>   inner1(&bl)
> end
>
> def outer12(&bl)
>   inner2(&bl)
> end
>
> def outer21
>   inner1 {yield}
> end
>
> def outer22
>   inner2 {yield}
> end
>
> def inner1(&bl)
>   bl.call
> end
>
> def inner2
>   yield
> end
>
> n = 100000
>
> Benchmark.bmbm(10) do |rpt|
>   rpt.report("outer11") do
>     n.times {outer11{}}
>   end
>
>   rpt.report("outer12") do
>     n.times {outer12{}}
>   end
>
>   rpt.report("outer21") do
>     n.times {outer21{}}
>   end
>
>   rpt.report("outer22") do
>     n.times {outer22{}}
>   end
> end
>
> __END__
>
> Output:
>
> Rehearsal ---------------------------------------------
> outer11     0.890000   0.010000   0.900000 (  0.894500)
> outer12     0.370000   0.000000   0.370000 (  0.364880)
> outer21     0.770000   0.000000   0.770000 (  0.776638)
> outer22     0.170000   0.000000   0.170000 (  0.163393)
> ------------------------------------ total: 2.210000sec
>
>                 user     system      total        real
> outer11     0.490000   0.000000   0.490000 (  0.491969)
> outer12     0.400000   0.000000   0.400000 (  0.396264)
> outer21     0.760000   0.000000   0.760000 (  0.764508)
> outer22     0.160000   0.000000   0.160000 (  0.161982)
>
>
> --
>       vjoel : Joel VanderWerf : path berkeley edu : 510 665 3407
>
>