On Mon, Sep 23, 2013 at 3:58 PM, Philippe <philw...@gmail.com> wrote:
> ** > I was told the QMap implementation was changed from Qt 4 to 5, to improve > performances... I guess some other tests give different results?... > I had a look at the commit logs. The commit that introduced this change states that it's done so that one can later add custom allocators. Here's an excerpt: <snip> The rewrite now uses a red-black tree, and all allocations and tree operations happen in the cpp file. This will allow us to introduce custom allocation schemes in later versions of Qt. </snip> As for performance, the commit itself mentions that this change increases insert/lookup times by 10-30%. Though in my tests, it was much slower. -mandeep > > Philippe > > On Mon, 23 Sep 2013 15:15:37 +0530 > Mandeep Sandhu <mandeepsandhu....@gmail.com> wrote: > > > > Actually, everything's a little slower with Qt5. Is C++11 enabled by > default? Could that be the cause of degraded performance? > >> >> Qt 5 uses RB tree in QMap >> > > Ah! That explains similar performance of QMap with std::map (though > iteration is slower than std::map). > > But why was RB tree used when it doesn't as well as the previous skiplist > based impl? > > -mandeep > > > >> >> -- >> Regards, >> Konstantin >> > > > > _______________________________________________ > Interest mailing list > Interest@qt-project.org > http://lists.qt-project.org/mailman/listinfo/interest > >
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