On Sat, Jan 17, 2009 at 6:11 AM, Konstantin Litvinenko <to.darkangel@gmail.com> wrote:
Hi!
I am developing an application with very intensive boost::filesystem::path usage. At certain moment application start to be slowly and I start profiler. Profiler shows me that std::map<fs:path, ....> is painfully slow due path::operator <() that do
lexicographical compare
, that do
void iterator_helper<Path>::do_increment( iterator & itr )
that is really slow.
So I have replaced std::map on boost::unordered_map.. and didn't get expected performance gain. Profiles show me that path::operator <() hit count 200000 and now only 100000. That tooooo much. Further investigation shows that problem was path::operator ==() used in unordered_map. I understand that operator == can be implemented using strict weak ordering concept, but for filesystem::path. Why not implement it as:
bool path::operator == (const path& lhs, const path& rhs) const { return lhs.string() == rhs.string(); }
Good question. While the other relationals have to use std::lexicographical_compare(), operators == and != can do a simple string compare, as you suggest. SVN trunk updated. It is a bit too late for these changes to make it into 1.38.0, however. It would be interesting if you could report back what impact that change has on you timings. Thanks, --Beman