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Date:      Wed, 19 Apr 2023 23:41:20 +0200
From:      Hans Petter Selasky <hselasky@freebsd.org>
To:        Jessica Clarke <jrtc27@freebsd.org>
Cc:        Brooks Davis <brooks@freebsd.org>, src-committers <src-committers@freebsd.org>, dev-commits-src-all@freebsd.org, dev-commits-src-main@freebsd.org
Subject:   Re: git: 8dcf3a82c54c - main - libc: Implement bsort(3) a bitonic type of sorting algorithm.
Message-ID:  <42d63675-9b1f-70dc-a1da-fef3d43790fd@freebsd.org>
In-Reply-To: <2840BE79-CC25-427A-A5E9-476A38E749E3@freebsd.org>
References:  <202304191206.33JC6Qcp062380@gitrepo.freebsd.org> <ZEAM3rO9r5e97BHE@spindle.one-eyed-alien.net> <a073fd36-9aa9-e988-0cc5-86af305fb654@freebsd.org> <3B5734C4-8630-4CD5-BA8D-DE33899161F1@freebsd.org> <e2ea5c89-aa48-e257-b9d5-7fe783bf216e@freebsd.org> <2840BE79-CC25-427A-A5E9-476A38E749E3@freebsd.org>

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On 4/19/23 22:17, Jessica Clarke wrote:
> pdqsort is n log n time, in-place and doesn’t allocate, and is used,
> for example, for Rust’s standard sort_unstable.

Hi Jessica,

Like many many people have tried over the years, to improve the belated 
QuickSort (*) algorithm since it was invented, by catching bad behaviour 
and then fallback to other algorithms, pdqsort() is not a solution!

Yes, it is probably "N log N" time, but if you read the code carefully, 
it falls back to heapsort(), which indeed uses malloc(), which is 
exactly my point, that I want to avoid.

Please come forward with a "N log N" time algorithm which is malloc() 
and alloca() free, and then we'll talk!

And not at least BSD-2-clause licensed and not covered by any patents, 
GPLv2 or whatever!

--HPS

(*) https://en.wikipedia.org/wiki/Quicksort




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