Re: define pg_structiszero(addr, s, r)
От | Bertrand Drouvot |
---|---|
Тема | Re: define pg_structiszero(addr, s, r) |
Дата | |
Msg-id | ZyDrFgYfRwRXWSmh@ip-10-97-1-34.eu-west-3.compute.internal обсуждение исходный текст |
Ответ на | Re: define pg_structiszero(addr, s, r) (Heikki Linnakangas <hlinnaka@iki.fi>) |
Список | pgsql-hackers |
Hi, On Tue, Oct 29, 2024 at 11:39:03AM +0200, Heikki Linnakangas wrote: > 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. Oh right. It looks like that moving the "scanf" within each loop "helps" and that both give pretty comparable results. Regards, -- Bertrand Drouvot PostgreSQL Contributors Team RDS Open Source Databases Amazon Web Services: https://aws.amazon.com
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