| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Greg Stark <gsstark(at)mit(dot)edu> |
| Cc: | Paul Matthews <plm(at)netspace(dot)net(dot)au>, pgsql-hackers(at)postgresql(dot)org |
| Subject: | Re: Slaying the HYPOTamus |
| Date: | 2009-08-23 05:42:36 |
| Message-ID: | 19346.1251006156@sss.pgh.pa.us |
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| Lists: | pgsql-hackers |
Greg Stark <gsstark(at)mit(dot)edu> writes:
> If there's a performance advantage then we could add a configure test
> and define the macro to call hypot(). You said it existed before C99
> though, how widespread was it? If it's in all the platforms we support
> it might be reasonable to just go with it.
For one data point, I see hypot() in HPUX 10.20, released circa 1996.
I suspect we would want a configure test and a substitute function
anyway. Personally I wouldn't have a problem with the substitute being
the naive sqrt(x*x+y*y), particularly if it's replacing existing code
that overflows in the same places.
regards, tom lane
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