Alright thanks! That is good news.
Alright thanks! That is good news.
No computation of division at runtimeCode:#include <iostream> template<int Num1, int Num2> struct divide { static const int value = Num1 / Num2; }; int main() { std::cout << divide<10, 5>::value << std::endl; }
Originally Posted by Adak
The only compiles that are too retarded to optimize out "10 / 5" are unlikely to be able to handle these advanced template constructs, I think. So I think it would be really bad to use a messy construct like this.No computation of division at runtimeCode:#include <iostream> * template<int Num1, int Num2> struct divide { static const int value = Num1 / Num2; }; int main() { std::cout << divide<10, 5>::value << std::endl; }
In fact, I find it more likely a compiler is unable to optimize something like divide<10, 5>*3 than it 10 / 5 * 3...
No one would write that, he's showing off
The point was that it will be optimized even in Debug mode. In Release, I'm sure the compiler will optimize it.
And any compiler that is able to instantiate a template like this will have no problems optimizing divide<10, 5> * 3.
And some might write like this, if not for exactly division, but for other things such as binary -> decimal or whatever.
Apples and oranges...
Specific to your example, you can't do a/b for any non-constant expressions a or b, something you should have really mentioned maybe. So yeah you're showing off, no one would write that.
The compiler can't optimize non-constant expressions to the results anyway, even without the template, so I figure it is kind of the same
No constant expressions = no optimization (unless it's SSE or the like).
How do you know the compiler doesn't already evaluate constant expressions in debug build? E.g with gcc:
Code:int a = 14 / 2;Code:.stabn 68,0,5,LM3-_main LM3: movl $7, -4(%ebp)
I might be wrong.
Quoted more than 1000 times (I hope).Thank you, anon. You sure know how to recognize different types of trees from quite a long way away.
Well, as I said, with optimizations on (ie Release build), then it 99% likely will.
But in Debug mode (ie no optimizations), it most likely will not (VC++ will not).
And if they aren't constant expressions, then neither will work very well (unless we talk about SSE & Co).
Then why optimize arithmetic in debug builds at all?
Because:
