Re: Slaying the HYPOTamus

From: Sam Mason <sam(at)samason(dot)me(dot)uk>
To: pgsql-hackers(at)postgresql(dot)org
Subject: Re: Slaying the HYPOTamus
Date: 2009-08-24 17:59:38
Message-ID: 20090824175938.GL5407@samason.me.uk
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On Mon, Aug 24, 2009 at 07:07:13AM -0700, David Fetter wrote:
> These next two lines are a teensy bit baroque. Is there some
> significant speed increase that would justify them?

Just noticed with your revised code that the following check:

> On Mon, Aug 24, 2009 at 11:14:19PM +1000, Paul Matthews wrote:
> > if (x == 0.0)
> > return 0.0;
> > else {
> > yx = y/x;

is preventing a divide by zero on the line above. So it's not a
performance hack, it's just allowing it to remain correct as a result of
changing the maths around.

> > return x*sqrt(1.0+yx*yx);
> > }
> > }

--
Sam http://samason.me.uk/

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