Phil Bouchard <philippe@fornux.com> wrote:
On 5/25/2011 3:27 PM, Nevin Liber wrote:
You have yet to explain why your make_auto is so much slower than new directly. It just isn't that expensive to copy one pointer and zero out another. I can't imagine what else your code can possibly be doing. I can't imagine how that can be more, let alone significantly more expensive than a heap allocation. Enlighten me.
Well if you have a direct assignment coming from operator new then the pointer can be transferred directly into a register. If you have temporary r-values to copy it into then the transfer will be done from one memory location to another, but it won't be a fast as a register-to-register transfer.
That effect should be immeasurably small, or eliminated entirely by the compiler. I think you had better post your benchmark code. There must surely be something else going on here. Phil.