-----Original Message----- From: boost-users-bounces@lists.boost.org [mailto:boost-users- bounces@lists.boost.org] On Behalf Of Eric Niebler Sent: Wednesday, October 10, 2007 3:04 PM To: boost-users@lists.boost.org Subject: Re: [Boost-users] Container iteration macro that is equivalent tohandcoded iteration?
Michael Marcin wrote:
Erik wrote:
Or is it possible to configure BOOST_FOREACH to be as efficient as
my macro?
I don't know but that is a good question.
I considered using BOOST_FOREACH until I checked its generated output... which was worse than std::for_each with a boost::bind which was worse than std::for_each with a hand coded functor which was worse than a hand coded for loop like yours above.
I won't deny that the abstraction penalty of BOOST_FOREACH is not zero, but have either of you actually measured the overhead? I have, and I found BOOST_FOREACH to be about 5% slower than the equivalent hand-coded loop when compiler optimizations are turned on. It's really very small, and that 5% buys you a lot of expressivity. YMMV.
-- Eric Niebler Boost Consulting www.boost-consulting.com _______________________________________________ Boost-users mailing list Boost-users@lists.boost.org http://lists.boost.org/mailman/listinfo.cgi/boost-users
Where does the 5% come from? Which part of BOOST_FOREACH (which is way to advanced for me to understand) is the part that causes the most trouble with compilers? Is it the extra if statement trick that seems to be used to initialize the variable? -- John