AMDG David Abrahams wrote:
I think the optimizer can remove some redundant tests if the functions are inlined. But, that said, I am becoming more and more convinced as this discussion goes on that compressing stacked iterator adaptors is barking up the wrong tree if you care about efficiency. The difference between the code generated in the abstracted case and the code you'd write by hand is simply too great.
No, I don't have a picture of a better solution yet. But it's an interesting problem.
Here are some measurements for my current version of filter_iterator In brief: 4 function objects containing two integers each: 3.39 seconds 4 stateless function objects: 2.813 seconds 4 stateless function objects combined using phoenix's && rather than stacked iterators: 2.563 seconds 1 stateless function object 2.015 seconds raw for loop using vector iterators 2.516 seconds raw for loop using pointers: 1.703 seconds These were all doing the same calculation over the same underlying vector. In Christ, Steven Watanabe