On Mon, Apr 10, 2006 at 04:18:56PM -0700, David Leimbach wrote:
> Interesting example...
>
> SomeContainer::iterator it = SomeContainerObject.begin();
>
> for (; it != SomeContainerObject.end(); ++it)
>
> is probably a lot faster than
>
> for(; it != SomeConatinerObject.end(); it++)
>
> And I'd bet that not much more than half of the so-called C++
> programmers out there in the world know why this is.
If the punch line here is, in fact, what I think it is, then
a good optimizing compiler should be able to make these two
pretty close in terms of performance.
I've been doing optimizing compilers at Sun for quite some time
now (C/C++ and Fortran) and one thing that I constantly talk
to our customers about is that in todays world of opaque CPU
design they actually don't know whether 'a = a + 1;' is slower
or faster than 'a++;'. So the best advice I can give them
is to:
1. Express semantics, not how to generate code
2. Pick a compiler vendor you can trust.
3. Make Performance Analysis part of your debugging.
Thanks,
Roman.
