Author: David Rasmussen
Date: 02:29:47 12/24/02
Go up one level in this thread
On December 23, 2002 at 21:33:50, Matt Taylor wrote: > >The biggest hit you take in C++ is virtual functions, and inevitably people use >them. The virtual functions are very damaging due to the fact that they're >implemented with a function pointer, and at the machine level it translates into >an indirect call. The indirect calls branch mispredict because the CPU can't >figure out ahead-of-time where you're calling to, and branch mispredicts are >expensive. > >Unfortunately, not using virtual functions (mostly) defeats the benefits you >would get from OO here. > First of all, that is a poor understanding of OO. Secondly, OO isn't the only virtue of C++. By far. You would only use virtual functions when you need polymorphism. And if you wanted to do that without virtual functions, you would need some other form of dispatch such as a switch statement. Many different tests shows that a function call and a switch statement isn't faster than a virtual function call. In fact it is slower. All of this doesn't matter, as there is no obligation to use virtual functions in a chess program to use C++ successfully. >If you convert to C++ without using virtual functions, you probably won't take >much of a hit at all. Personally, I've never seen a -need- to convert to C++. I see no need to use an inferior language to express the same thing for no gain at all. C++ gives my type safety, better I/O and a lot more. >I >can implement my OO in C, and it simplifies linking because C doesn't have name >mangling. > Is that an issue? It hasn't been an issue for me at all. /David
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