Re: [Boost-users] [GIL] Performance warning...

Subject: Re: [Boost-users] [GIL] Performance warning...
From: Eloi Du Bois (eloi.du.bois_at_[hidden])
Date: 2009-11-27 18:37:15

I am not an expert but I think on primitive types, there is no need to put a
reference (and it may slows down the process).
But the line I mentioned before concern a channel object, and I think this
object stores many datas (maybe a byte array ?).

2009/11/28 Christian Henning <chhenning_at_[hidden]>

> Lubomir, looking at the default_channel_converter the channels already
> arrive as a const reference. All I did was to make sure they are still
> const references in the channel_converter functions. In all cases the
> source channels should at least be const. Which allows for more
> compiler optimizations.
>
> I did run the performance test in gil_test suite and the changes were
> marginal. Some tests were faster some were slower after the change.
>
> Christian
>
> On Fri, Nov 27, 2009 at 6:13 PM, Lubomir Bourdev <lbourdev_at_[hidden]>
> wrote:
> > This was done on purpose. I don't know if it still holds, but it used to
> be
> > that a const reference to a simple type like an int or char is slower
> than
> > passing the type by value. This is the same reason most STL algorithms
> take
> > iterators by value. If you want to make this change it is important to
> > verify that performance of simple built-in channel types is not adversely
> > affected.
> >
> > Lubomir
> >
> > On 11/27/09 12:17 PM, "Christian Henning" <chhenning_at_[hidden]> wrote:
> >
> >> Hi Eloi, you're correct and I'll fix that. I can even make it const
> >> reference. Running the test shows no real difference but that might be
> >> only because no expensive channels are being used.
> >>
> >> I'll commit the changes asap.
> >>
> >> Lubomir, please review the changes if your time allows. Affected files
> >> are channel_algorithm.hpp and gil_concept.hpp.
> >>
> >> Thanks,
> >> Christian
> >>
> >
> >
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