Re: [boost] [function] Merits of drop-in replacement

From: Tobias Schwinger (tschwinger_at_[hidden])
Date: 2007-09-17 15:23:11

Doug Gregor wrote:
> On Sep 14, 2007, at 4:05 PM, Michael Marcin wrote:
> 
>> I ran across http://www.codeproject.com/cpp/fastdelegate2.asp the  
>> other
>> day.  I searched the archives and didn't find any discussion about  
>> it on
>> the list.
>>
>> It makes some good arguments and seems to be done pretty well,  
>> although
>> it may have succumb to a bit of feature creep.
>>
>> Should those benchmarks be reran against the trunk version of
>> Boost.Function?
> 
> Yes, those tests should certainly be rerun now that Boost.Function  
> does the small-object optimization. Copy performance for such small  
> objects is much, much improved.

I once hacked a quick benchmark to compare dispatch times of 
Bind&Function (1.34 versions) vs. FastDelegate.

With an inlineable replacement for 'boost::mem_fn' (accepting the member 
function pointer as a non-type template argument)

     http://tinyurl.com/37tkap

FastDelegate turned out to be (not quite) twice as fast as Function&Bind 
with MSVC, which isn't that much IMO held against the lost flexibility, 
such as not being able to use arbitrary function objects and only 
binding 'this'.

However, things looked quite a bit worse with GCC (version 4 IIRC, don't 
remember the exact numbers), a good chunk of it because of not-optimized 
compile-time const member pointers.

So FastDelegate is still be several times faster when it comes to member 
function pointers that are runtime values...

Regards,
Tobias