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From: Nathan Bossart <nathandbossart@gmail.com>
To: Ants Aasma <ants.aasma@cybertec.at>
Cc: Alvaro Herrera <alvherre@alvh.no-ip.org>
Cc: Amonson, Paul D <paul.d.amonson@intel.com>
Cc: Tom Lane <tgl@sss.pgh.pa.us>
Cc: David Rowley <dgrowleyml@gmail.com>
Cc: Andres Freund <andres@anarazel.de>
Cc: Shankaran, Akash <akash.shankaran@intel.com>
Cc: Noah Misch <noah@leadboat.com>
Cc: Matthias van de Meent <boekewurm+postgres@gmail.com>
Cc: pgsql-hackers@lists.postgresql.org <pgsql-hackers@lists.postgresql.org>
Subject: Re: Popcount optimization using AVX512
Date: Thu, 4 Apr 2024 12:28:40 -0500
Message-ID: <20240404172840.GB3866970@nathanxps13> (raw)
In-Reply-To: <CANwKhkO9RS_O2H4oeaXzfmBanXFeETq9de7Fuw5kkTLGAQJEvw@mail.gmail.com>
References: <20240401011708.GA2128739@nathanxps13>
	<202404011106.y4fci35kzdqt@alvherre.pgsql>
	<20240401155338.GA2296072@nathanxps13>
	<CANwKhkM-YZGE527y00LPU1660GW6zicvX7a=ZOsxnYYU0hng3g@mail.gmail.com>
	<20240401213140.GA2362108@nathanxps13>
	<CANwKhkNs9WnqCZDV3bKgaqZix0_NC1T=wf77=k4jYgG=Qr-vzw@mail.gmail.com>
	<20240403225029.GA3851411@nathanxps13>
	<CANwKhkO9RS_O2H4oeaXzfmBanXFeETq9de7Fuw5kkTLGAQJEvw@mail.gmail.com>

On Thu, Apr 04, 2024 at 04:02:53PM +0300, Ants Aasma wrote:
> Speaking of which, what does bumping up the inlined version threshold
> to 16 do with and without AVX-512 available? Linearly extrapolating
> the 2 and 4 byte numbers it might just come ahead in both cases,
> making the choice easy.

IIRC the inlined version starts losing pretty quickly after 8 bytes.  As I
noted in my previous message, I think we have enough data to switch to your
approach already, so I think it's a moot point.

-- 
Nathan Bossart
Amazon Web Services: https://aws.amazon.com





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