I was reading the book about "Core Techniques and Algorithms for Game Programming" - it suggested that for a class (say a soldier) with many instances of it - say 100+ soldiers that the code that is common to all the soldiers - ie the Draw function and AI function can be stored in one single instance of a class - called a FlyWeight to save memory. The soldier class would then simply have its unique values for each soldier - eg position, velocity, health. This way we only have one instance of the Draw and AI and saving us loads of memory. Note how this is different from having a soldier class derived from a generic soldier class that would contain the Draw and AI functions (*) However, my question is for the second case (*): Will the memory the compiler will create of the 100+ soldiers be (approx) 100 times the size of the soldier class ? I would have thought that the compiler would be clever enough to just have one instance of the generic code ? Thanks Adrian

The functions do not factor into the size of the class. Take a class Foo:

class Foo{private:   int Data;public:   void DoStuff( );};

The function DoStuff will actually be implemented as if you had written it like this:

struct Foo{   int Data;};void DoStuff(Foo* this){    //Do Stuff}

So implementing functions in a seperate class will save no memory whatsoever.

Above: Unless they are talking abou virtual functions.

Note that virtual functions will add a mere 4 bytes (assuming you're using 32-bit memory address anyway) to your class (a pointer to the vtable).

thanks, that was helpful,

cheers