C++Talk.NET C++ language newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  pure virtual function calls / optimization          C++Talk.NET Forum Index -> C++ language (comp.lang.c++) View previous topic :: View next topic   Author Message Guest Posted: Thu Jul 27, 2006 9:10 am    Post subject: pure virtual function calls / optimization Hi I wonder if their will be a performance penalty in the following situation due to virtual function calls: class Interface { public: virtual void methodA() = 0; virtual void methodB() = 0; virtual void methodC() = 0; virtual void methodD() = 0; }; class Implementation { public: void methodA() { /* do someting */ } void methodB() { /* do someting */ } void methodC() { /* do someting */ } void methodD() { /* do someting */ } }; IMHO there is no need for class Implementation to have a virtual method table, since there is just one possibility for every method. It's a special case, I know. Other derived classes may have virtual functions. What do current compilers do? Are there optimizations for such situations or did I just miss something? regards, Alex Back to top Guest Posted: Thu Jul 27, 2006 9:10 am    Post subject: Re: pure virtual function calls / optimization alexander.stippler@uni-ulm.de schrieb: Quote: Hi I wonder if their will be a performance penalty in the following situation due to virtual function calls: class Interface { public: virtual void methodA() = 0; virtual void methodB() = 0; virtual void methodC() = 0; virtual void methodD() = 0; }; class Implementation { public: void methodA() { /* do someting */ } void methodB() { /* do someting */ } void methodC() { /* do someting */ } void methodD() { /* do someting */ } }; IMHO there is no need for class Implementation to have a virtual method table, since there is just one possibility for every method. It's a special case, I know. Other derived classes may have virtual functions. What do current compilers do? Are there optimizations for such situations or did I just miss something? regards, Alex Sorry, of course the Implementation class is publicly derived from the Interface class. class Implementation : public Interface { //... }; Back to top Ian Collins Guest Posted: Thu Jul 27, 2006 9:11 am    Post subject: Re: pure virtual function calls / optimization alexander.stippler@uni-ulm.de wrote: Quote: Hi I wonder if their will be a performance penalty in the following situation due to virtual function calls: class Interface { public: virtual void methodA() = 0; virtual void methodB() = 0; virtual void methodC() = 0; virtual void methodD() = 0; }; class Implementation { public: void methodA() { /* do someting */ } void methodB() { /* do someting */ } void methodC() { /* do someting */ } void methodD() { /* do someting */ } }; IMHO there is no need for class Implementation to have a virtual method table, since there is just one possibility for every method. It's a special case, I know. Other derived classes may have virtual functions. What do current compilers do? Are there optimizations for such situations or did I just miss something? The may well be an over head, but it will be small. Whether or not the compiler can perform any optimisations such as inlining depends on the compiler and the use of the functions. -- Ian Collins. Back to top Display posts from previous: All Posts1 Day7 Days2 Weeks1 Month3 Months6 Months1 Year Oldest FirstNewest First         C++Talk.NET Forum Index -> C++ language (comp.lang.c++) All times are GMT Page 1 of 1   Jump to: Select a forum C/C++----------------C LanguageC Language (Moderated)C++ Language (Moderated)C++ language (comp.lang.c++)C++ language, library and standards Non-English C/C++ Newsgroups----------------C++ (German)C++ (French)  You cannot post new topics in this forum You cannot reply to topics in this forum You cannot edit your posts in this forum You cannot delete your posts in this forum You cannot vote in polls in this forum Powered by phpBB © 2001, 2006 phpBB Group SEO toolkit © 2004-2006 webmedic.