Re: speed versus OO
On 2008-01-27 00:24, michael.goossens@gmail.com wrote:
For instance take: heavely used classes, lets say Vector(not the
dynamic datatype but a mathematical vector) and Point. They have both
3 class variables x, y and z and some functions they both use.
Now the question is, would subclassing these 2 classes have any
negative effect on the speed of a program that uses these classes very
frequently, i.e. the raytracer I'm building. So completely different
types of classes versus inheritance, which would be faster? Or doesn't
it matter.
Maybe, the effects of inheritance will depend on the classes that you
inherit from and the class that inherits. In some situations there is no
difference in speed in other there are.
My thought would be that its slower and the only gain is that its
easier in a conceptual way to use inheritance, but I don't need a good
design in the first place, I need speed!
I'm most likely not going to use inheritance for that reason but also
because those classes "have" to be differentiated from eachother. By
that I mean they can't just take over eachothers identity. Normal n =
v with v a Vector may not be possible, even used explicit to make
sure, and this kind of concretisation is what one loses by the
abstraction of the superclass no? Or is it my responsability not to
lose the identity of a class into the abstraction of the superclass.
I am not an expert on the subject but I have done some programming
involving 3D and I never found a reason to not use a single vector-class
for vectors, normals, and points. In fact using different types can lead
to inefficiencies if you need to convert between them often (i.e. if a
normal is not a vector you can not calculate the dot-product of it an
another vector and would need to create a vector of it first, sometimes
you want the vector from the origin to a point, again you would have to
create the vector). If you can not tell a normal from a point in your
code it means you use bad names for your variables.
--
Erik Wikstr?m