From: Daniel Nugent <nugend@...>
Date: 2006-02-15T22:58:07+09:00
Subject: Re: Rescuing blocks?

Pat: I think it already does and there's still a performance hit. 
Though Eric's machine chugs a little more than mine, I'd be interested
to see what his ratios are with this added benchmark:

require 'benchmark'

N = 10_000_000

Benchmark.bmbm do |b|
  b.report 'begin' do
    N.times { begin; rescue; end }
  end

  b.report 'begin no rescue' do
    N.times { begin; end }
  end

  b.report 'no begin' do
    N.times { }
  end
end




G:\Documents and Settings\Dan Nugent\Desktop>ruby -v rescue.rb
ruby 1.8.4 (2005-12-24) [i386-mswin32]
Rehearsal ---------------------------------------------------
begin             3.703000   0.000000   3.703000 (  3.844000)
begin no rescue   3.125000   0.000000   3.125000 (  3.281000)
no begin          2.078000   0.000000   2.078000 (  2.172000)
------------------------------------------ total: 8.906000sec

                      user     system      total        real
begin             4.703000   0.000000   4.703000 (  4.906000)
begin no rescue   3.203000   0.000000   3.203000 (  3.312000)
no begin          2.047000   0.000000   2.047000 (  2.141000)

G:\Documents and Settings\Dan Nugent\Desktop>

On 2/15/06, Patrick Hurley <phurley@gmail.com> wrote:
> On 2/15/06, Eric Hodel <drbrain@segment7.net> wrote:
> > On Feb 14, 2006, at 9:50 PM, Hal Fulton wrote:
> >
> > > Dave Cantrell wrote:
> > >> Eric Hodel wrote:
> > >>>
> > >>> You're going to get a performance hit setting up an exception
> > >>> trap this way.
> > >> Time for some down-South edumucation. What kind of performance hit
> > >> are we talking about here? And why the hit at all?
> > >> (I seem to recall reading somewhere once upon a time about memory
> > >> stack stuff, but I'm not an old-school C-programmer so I never had
> > >> to deal with it --- unfortunately for me...)
> > >
> > > Well, my knowledge is limited. Someone else can answer better.
> > >
> > > But look at it from a common-sense standpoint. Exceptions aren't
> > > magic. Everything Ruby does can be done in assembly language, it's
> > > just more verbose.
> > >
> > > I would think that exceptions, at the lowest level, work something
> > > like:
> > >
> > >    if something_happened_here
> > >       goto the_place_where_exceptions_are_caught
> > >
> > > So at the very least, catching exceptions means that you're doing
> > > some sort of comparison or conditional branch. And this is code
> > > that doesn't have to be run/generated *unless* you are catching
> > > exceptions.
> >
> > Yes.  You get a setup/teardown of an exception handler for every
> > block.  Right now class module and def have an implicit exception
> > handler built in.  Adding a begin; rescue; end explicitly to blocks
> > gives you a very hefty penalty.  That's no guarantee of similarly bad
> > performance with an implicit exception handler, but it still won't be
> > free.
> >
> > I've very rarely found myself placing an exception handler directly
> > inside a block so I don't think it would be worth it.
> >
> > $ cat rescue.rb
> > require 'benchmark'
> >
> > N = 10_000_000
> >
> > Benchmark.bmbm do |b|
> >    b.report 'begin' do
> >      N.times { begin; rescue; end }
> >    end
> >
> >    b.report 'no begin' do
> >      N.times { }
> >    end
> > end
> >
> > $ ruby -v rescue.rb
> > ruby 1.8.4 (2005-12-24) [powerpc-darwin8.4.0]
> > Rehearsal --------------------------------------------
> > begin      6.330000   0.060000   6.390000 (  8.303914)
> > no begin   2.580000   0.010000   2.590000 (  3.178967)
> > ----------------------------------- total: 8.980000sec
> >
> >                 user     system      total        real
> > begin      6.320000   0.060000   6.380000 (  8.597418)
> > no begin   2.570000   0.020000   2.590000 (  3.526030)
> >
> > --
> > Eric Hodel - drbrain@segment7.net - http://segment7.net
> > This implementation is HODEL-HASH-9600 compliant
> >
> > http://trackmap.robotcoop.com
> >
> >
> >
> >
>
> Sure, but couldn't the parser "flag" blocks that have the exception
> handler and only provide support for those cases? I do not see why we
> would have to pay the price on every block -- of course you have the
> over head when you use it.
>
> pth
>
>


--
-Dan Nugent