From: Markus Wichmann <nullplan@gmx.net>
To: musl@lists.openwall.com
Subject: Re: Wrong info in libc comparison
Date: Sat, 16 Sep 2017 20:38:24 +0200 [thread overview]
Message-ID: <20170916183824.6i6m2chfwgyvslzp@voyager> (raw)
In-Reply-To: <20170916161802.GY1627@brightrain.aerifal.cx>
On Sat, Sep 16, 2017 at 12:18:02PM -0400, Rich Felker wrote:
> Even non-naive quicksort has O(n²) time; there is a way to avoid this
> with an esoteric efficient algorithm for finding the median to use as
> the pivot, but nobody does it because the constant is so bad. The only
> known practical way to avoid the n² worst-case is some kind of
> introsort. So "naive" is really only about the problem of blowing up
> the stack.
>
Oh crap, yes, I forgot about that. Median-of-three only solves the
quadratic time problem on sorted inputs but quadratic sequences still
exist. My bad.
> I agree something like "mergesort+quicksort" sounds good, but just to
> make sure, was mergesort already in use in the glibc version in the
> comparison? i.e. can I make this fix without inconsistently reflecting
> information from different glibc versions?
>
> Rich
Yes, I previously looked at glibc 2.19 and it had the same code.
Apparently, the files are really old with only minor changes over the
years. At least, that's what I gathered from the changelogs.
Ciao,
Markus
prev parent reply other threads:[~2017-09-16 18:38 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-09-13 13:51 Markus Wichmann
2017-09-13 18:10 ` Rich Felker
2017-09-13 18:51 ` Markus Wichmann
2017-09-13 19:25 ` Szabolcs Nagy
2017-09-13 19:53 ` Rich Felker
2017-09-15 19:18 ` Markus Wichmann
2017-09-16 9:37 ` Szabolcs Nagy
2017-09-16 14:01 ` Markus Wichmann
2017-09-16 17:11 ` Szabolcs Nagy
2017-09-16 19:34 ` Markus Wichmann
2017-09-16 16:18 ` Rich Felker
2017-09-16 18:38 ` Markus Wichmann [this message]
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