Date: Fri, 15 Sep 2017 21:18:46 +0200 From: Markus Wichmann <nullplan@....net> To: musl@...ts.openwall.com Subject: Re: Wrong info in libc comparison On Wed, Sep 13, 2017 at 03:53:06PM -0400, Rich Felker wrote: > If you're considering big-O, where n->infinity (or at least to the > largest value that can fit in memory), malloc most certainly has > failed (because the array to be sorted already filled memory) and > you're looking at the "fallback" case. > I think we're getting sidetracked here. Every libc worth its salt uses a loglinear sorting algorithm. Thus they are all equal in that regard. Only exception to this I've ever seen is uclibc, which uses Shell sort with Pratt's sequence, which is O(sqrt(n^3)) instead (is there a snappy term for this complexity?) Besides, big-O is also about the behavior of time on change of space (what happens if the problem doubles in size?). > Maybe the comparison of sort algorithm used is interesting for reasons > other than just big-O though, in which case mentioning the "merge > (when it fits in memory)" would probably be helpful. > > Rich Algorithms can be compared on a number of metrics, and just the name doesn't tell us much (e.g. quicksort with naive "first element" pivot selection has a pathological case on sorted input, while quicksort with med3 pivot selection handles that very well). If you really want to know something specific, you'll have to look it up in source, anyway. But, if you do give a name, make sure it's the right one. Ciao, Markus
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