From: Steinar H. Gunderson <sgunderson@bigfoot.com>
To: pgsql-performance@postgresql.org
Subject: Re: New to PostgreSQL, performance considerations
Date: Mon, 11 Dec 2006 14:34:00 +0100
Message-ID: <20061211133400.GA25821@uio.no> (raw)
In-Reply-To: <8a0c7af10612110509r7b1d5a5er68d4efd32c8c0e1e@mail.gmail.com>
References: <8a0c7af10612101141n2c7727c3r2f92345753960808@mail.gmail.com>
<430d92a20612101336r3de8862coe618277fccb4006a@mail.gmail.com>
<8a0c7af10612101702i49b5a533v4a2300d90d9dae6b@mail.gmail.com>
<20061211021847.GE16692@mathom.us>
<8a0c7af10612110305u305124b2v3d63491b5f57a86b@mail.gmail.com>
<20061211112547.GA24571@uio.no>
<8a0c7af10612110509r7b1d5a5er68d4efd32c8c0e1e@mail.gmail.com>
On Mon, Dec 11, 2006 at 11:09:13AM -0200, Daniel van Ham Colchete wrote:
>> You know what? I don't.
> So test it yourself.
You're making the claims, you're supposed to be proving them...
> As I said, it is an example. Take floatpoint divisions. You have
> plenty of ways of doing it: 387, MMX, SSE, 3dNow, etc... Here GCC have
> to make a choice.
No, you don't. MMX, SSE and 3Dnow! will all give you the wrong result
(reduced precision). SSE2, on the other hand, has double precision floats, so
you might have a choice there -- except that PostgreSQL doesn't really do a
lot of floating-point anyhow.
> And this is only one case. Usually, compiler optimizations are really
> complex and the processor's timings counts a lot.
You keep asserting this, with no good backing.
> If you still can't imagine any case, you can read Intel's assembler
> reference. You'll see that there are a lot of ways of doing a lot of
> things.
I've been programming x86 assembler for ten years or so...
> Steinar, you should really test it. I won't read the PostgreSQL source
> to point you were it could use SSE or SSE2 or whatever. And I won't
> read glibc's code.
Then you should stop making these sort of wild claims.
> You don't need to belive in what I'm saying. You can read GCC docs,
> Intel's assembler reference, AMD's docs about their processor and
> about how diferent that arch is.
I have.
/* Steinar */
--
Homepage: http://www.sesse.net/
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To: pgsql-performance@postgresql.org
Cc: sgunderson@bigfoot.com
Subject: Re: New to PostgreSQL, performance considerations
In-Reply-To: <20061211133400.GA25821@uio.no>
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