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From: Heikki Linnakangas <[email protected]>
To: Bertrand Drouvot <[email protected]>
To: Peter Smith <[email protected]>
Cc: Peter Eisentraut <[email protected]>
Cc: [email protected]
Subject: Re: define pg_structiszero(addr, s, r)
Date: Tue, 29 Oct 2024 11:39:03 +0200
Message-ID: <[email protected]> (raw)
In-Reply-To: <ZyCUsIu/[email protected]>
References: <[email protected]>
	<[email protected]>
	<ZusioyiXTyKpOP/[email protected]>
	<[email protected]>
	<ZyCUsIu/[email protected]>

On 29/10/2024 09:54, Bertrand Drouvot wrote:
>> https://godbolt.org/z/x9hPWjheq.
> 
> Yeah, I also think that's fine. Peter Smith did some testing in [1] comparing
> memcmp and simple loop checking (thanks Peter for the testing!):
> 
> "
> Iterate 1000000 times...
> check zeros using loop -- elapsed=0.041196s
> check zeros using memcmp -- elapsed=0.016407s
> "
> 
> So, in this test, the loop is 0.024789s longer means 0.024789s/1000000=24 Nanosecond
> slower per comparison (If my math is correct).

I believe that test program is bogus. Look at the assembly code; the 
compiler optimized away the loops.

-- 
Heikki Linnakangas
Neon (https://neon.tech)

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