is speed of exec of a member function always impacted by an extra layer in a class hierarchy?

[er]

hi,

what if i have
class B{public: virtual void f()const=0;};
class D0: public B{/*empty */};
class D1: public B{/*empty */};

is the execution of f slower for
class A: public D0{public: virtual void f()const;}
than it is for
class A: public B{public: virtual void f()const;}
given that their implementations for f are the same?

i'm aware that
http://www.parashift.com/c++-faq-lite/virtual-functions.html says:
"The compiler creates a v-table for each class that has at least one
virtual function."
but the reason i have a doubt is that D0 and D1 are used only to
specify two abstract sub-hierarchies.

 

[Victor Bazarov]

what if i have
class B{public: virtual void f()const=0;};
class D0: public B{/*empty */};
class D1: public B{/*empty */};

is the execution of f slower for
class A: public D0{public: virtual void f()const;}
than it is for
class A: public B{public: virtual void f()const;}
given that their implementations for f are the same?

Should be no difference.

i'm aware that
http://www.parashift.com/c++-faq-lite/virtual-functions.html says:
"The compiler creates a v-table for each class that has at least one
virtual function."
but the reason i have a doubt is that D0 and D1 are used only to
specify two abstract sub-hierarchies.

Shouldn't matter.

V

 

[Alex Vinokur]

hi,

what if i have
class B{public: virtual void f()const=0;};
class D0: public B{/*empty */};
class D1: public B{/*empty */};

is the execution of f slower for
class A: public D0{public: virtual void f()const;}
than it is for
class A: public B{public: virtual void f()const;}
given that their implementations for f are the same?

[snip]

Look at
http://article.gmane.org/gmane.comp.lang.c++.perfometer/66

 

[er]

hi,

what if i have
class B{public: virtual void f()const=0;};
class D0: public B{/*empty */};
class D1: public B{/*empty */};

is the execution of f slower for
class A: public D0{public: virtual void f()const;}
than it is for
class A: public B{public: virtual void f()const;}
given that their implementations for f are the same?

[snip]

Look athttp://article.gmane.org/gmane.comp.lang.c++.perfometer/66

--
Alex Vinokur
email: alex DOT vinokur AT gmail DOT com
http://mathforum.org/library/view/10978.html
http://sourceforge.net/users/alexvn

interesting. thanks.