markg added a comment.
In D10857#214867 <https://phabricator.kde.org/D10857#214867>, @jtamate wrote: > In D10857#214607 <https://phabricator.kde.org/D10857#214607>, @dfaure wrote: > > > I'm not opposed to the idea, but measuring CPU usage is a rather misleading indicator. What if it takes 10 times longer, because it's progressing much more slowly? ;) > > > > Please at least measure with QElapsedTimer around the sorting (not to be committed, just to gather numbers about the actual performance of this from a user's point of view). > > I'm interested in the result ;) > > > The results are strange. All the results are measured sorting 50.000 small files: > > Both Qt are the same version from opensuse. > > In an i5, why the difference is so big? recent cpu bugs? > qSort in i3 > 274764, 276060 (with 3 directories), 365878, 424506 (without directories) > std::sort in i3 > 940, 995 (with 3 directories), 2472, 2539 (without directories) > > In AMD the results are closer, qSort wins > qSort in AMD > 658, 726, 695, 683, 676, 666, 649, 684, 666 (without directories) > std:sort in AMD > 843, 839, 878, 896, 925 (without directories) That surprises me a lot! I "thought" qSort was just a template or alias to std::sort, but it isn't: http://code.qt.io/cgit/qt/qtbase.git/tree/src/corelib/tools/qalgorithms.h#n340 But it isn't which kinda makes my other expectations moot (qSort == std::sort... it isn't) So i did some tests as well. 50000 filenames sorting them (computer sorting, not the natural one) with std::string and QString (yes, it matters) Filenames, well, sorta.. Made them up in a loop :) QString version: https://p.sc2.nl/r1JTFaf_z qSort: ~220ms std::sort ~276ms std::string version: https://p.sc2.nl/HJ69Y6G_G qSort: ~100ms std::sort ~130ms Note that std::string might not be the fair comparison as it's 8 bit/char. QString is 16. My compiler (in this rare case) Visual Studio 2017 on an Intel CPU. I still think it's wise to replace all qSort, if only for it being deprecated. But it does suck a little that qSort beats std::sort. REPOSITORY R241 KIO REVISION DETAIL https://phabricator.kde.org/D10857 To: jtamate, #frameworks, dfaure Cc: markg, apol, michaelh
