On Thu, Nov 21, 2013 at 5:38 PM, Joaquin M Lopez Munoz <joaquin@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. Unfortunately, it's not easy to share the actual BMI definition, which uses intermediary templates for the index definitions (for reuse in other BMIs), a custom extractor of the name to work-around VC "thunk" warnings (since name() is a pure virtual method), and the string-type is a legacy custom one. 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). Thanks for confirming it should not matter. I'll try with different sets of names in the index (the one I'm using now is very special), and I will confirm the same ranges are returned. --DD