Dominique Devienne <ddevienne <at> gmail.com> writes:
On Thu, Nov 21, 2013 at 5:38 PM, Joaquin M Lopez Munoz <joaquin <at>
tid.es> wrote:
Dominique Devienne <ddevienne <at> gmail.com> writes:
[...] to obtain this "range", I initially used (pseudo-code):
auto begin = by_name_index().lower_bound(prefix + " 0"); auto end = by_name_index().upper_bound(prefix + " 9");>> [...] I
switched to using instead:>
auto begin = by_name_index().lower_bound(prefix + " 0"); auto end = by_name_index().lower_bound(prefix + " :");> And this performs much better (20x). There is no reason why it should, if both ops are returning the same range. Could you please show the custom comparison predicate you're using? This might shed some light on the issue.
Thanks Joaquín.
[...]
I do not specify a custom comparison predicate to the BMI for name(), so it relies on std::less and calls the custom op< of our string type, which calls strncmp after some null checks. So it's a strict "ascii" lexicographical order, no locale used, and I'm confident it's ordering things correctly (it's been in place for months/years).
OK, this gives extra info: I thought you were using a custom comparator to test for prefix-equality --now I see you aren't, but instead you just rely on plain regular string comparison. So,consider typedef multi_index_container< std::string, indexed_by< ordered_non_unique<identity<std::string>> >
multi_t;
multi_t c={ "a 0","a 000","a 1","a 9","a 90","a :" }; The following auto first=c.lower_bound("a 0"); auto last=c.upper_bound("a 9"); while(first!=last)std::cout<<*first++<<", "; produces the output a 0, a 000, a 1, a 9 while this auto first=c.lower_bound("a 0"); auto last=c.lower_bound("a :"); while(first!=last)std::cout<<*first++<<", "; produces a 0, a 000, a 1, a 9, a 90, See the difference? Is this related to your problem? Joaquín M López Muñoz Telefónica Digital