Efficient dynamic dispatch without virtual function tables: the SmallEiffel compiler

[Craig Black]

"bearophile" <bearophileHUGS at lycos.com> wrote in message 
news:fqs79a$26cq$1 at digitalmars.com...
> Craig Black:
>>Some more dispatch sites are removed after the type inference algorithm 
>>has been performed,
>
> ShedSkin has one of the most powerful type inference engines around, but 
> it gets rather slow. So the things you say too probably require a cost in 
> compile time.
>
>
>> Virtual function calls are a common bottleneck iobject-oriented code.
>
> Do you have any static to support what you say here? I have read an 
> article that says that in typical OOP C++ code virtual calls slow down 
> code by not too much:
> "The Direct Cost of Virtual Function Calls in C++" (1996, oldish):
> http://www.cs.ucsb.edu/~urs/oocsb/papers/oopsla96.pdf
>
> Bye,
> bearophile

As far as hardware is concerned, the longer the pipelines, the worse the 
penalty for virtual functions.  And modern Intel CPU's have incredibly long 
pipelines.  I do a lot of OOP and know from experience how bad this 
bottleneck can become.  Reducing the number of virtual functions for optimal 
performance is a big pain in the ass.

Here's an article that talks about reducing virtual function calls in C++. 
It talks specifically about doing this for game AI.

http://aigamedev.com/programming-tips/optimize-virtual-functions

-Craig