On Jul 8, 3:32 pm, Ulrich Eckhardt <eckha...@satorlaser.com> wrote:
Mycroft Holmes wrote:
Is there any reason why a function-pointer jump would be faster than an
enum-based switch?
In the best case, a switch can check if the argument is in a certain range
and then dispatch that range via a table. In the worst case, it generates a
series of if-then-else constructs which mess up dispatch speed.
right, but I assume the best case (the goto-dispatch) would be faster
than dereferencing a function pointer and passing arguments.
so, if I trust the optimizing compiler, I should leave the code as is.
BTW: I don't buy the argument that the enum is "conceptually public", at
least nothing in the example makes it that. If you make it private, you can
restrict the range of values it can take (encapsulation).
this is slightly off topic: believe it or not, the enum is public for
some good reason.
roughly speaking, this is a local class, so public/private makes very
little difference.
even more sense. Basically that structure would be like a vtable, only that
it can be changed at runtime.
yup, but we don't need trampolines here, we just need maximum speed.
Are you actually working on a specific performance problem that has already been diagnosed with the bottleneck being in this
switch-case? Or are you just theorizing that it could be made faster in some way, and you want to do so because this code is time
The VC++ compiler optimizer is very good, and if you use PGO, you can get the best results for your specific application. I don't