Does Virtual Function Impact on the efficiency of program

( In this program,
they both 2 times ). In this program, which is the better one
( efficiency )?

For OO design, I like using virtual member function.But considering
efficiency, template is better.

For OO design, I like using virtual member function.But considering
efficiency, template is better. Look at this program,
>
class Animal
{
public:
virtual void Walk() = 0;
};
>
class Dog
{
public:
virtual void Walk()
{
// ...
}
};
>
Virtual member function will make our object adding a virtual table
pointer( size: 4 ).When using Virtual member function, computer must
read the pointer value, and then find the virtual table.
>
// use template
template <SonClassType>
class Animal
{
public:
void Walk()
{
return static_cast<SonClassType*>(this)->WalkMe();
}
};
>
class Dog : public Animal <Dog>
{
public:
void WalkMe()
{
// ....
}
};
>
Using template , you call the Walk(), and then WalkMe() is called,
So It is also two times. Some books say virtual function will
Impact on the efficiency of program, so I cannot understand( In
this program, they both 2 times ). In this program, which is the
better one ( efficiency )?

For OO design, I like using virtual member function.But considering
efficiency, template is better. Look at this program,

Virtual member function will make our object adding a virtual table
pointer( size: 4 ).When using Virtual member function, computer must
read the pointer value, and then find the virtual table.

Using template , you call the Walk(), and then WalkMe() is called, So
It is also two times. Some books say virtual function will Impact on
the efficiency of program, so I cannot understand( In this program,
they both 2 times ). In this program, which is the better one
( efficiency )?

>
Virtual functions do come with a slight penalty but in most cases it is
negligible. A rule of thumb is to not make functions virtual unless you
have to (i.e. you need to override them in a derived class) but don't be
afraid to do so when you have to.
>