| From: | Greg Stark <stark(at)mit(dot)edu> |
|---|---|
| To: | amborodin(at)acm(dot)org |
| Cc: | Heikki Linnakangas <hlinnaka(at)iki(dot)fi>, Михаил Бахтерев <mob(at)k(dot)imm(dot)uran(dot)ru>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org>, Alexander Korotkov <a(dot)korotkov(at)postgrespro(dot)ru>, Михаил Бахтерев <mike(dot)bakhterev(at)gmail(dot)com> |
| Subject: | Re: GiST penalty functions [PoC] |
| Date: | 2016-09-09 18:40:59 |
| Message-ID: | CAM-w4HNf34gYFKug2Q2gnbpA8hDvtTbhrNoqMHgYD0za=M0yPg@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Thu, Sep 8, 2016 at 9:29 AM, Andrew Borodin <borodin(at)octonica(dot)com> wrote:
>>autoconf check for IEEE 754 floats
> Autoconf man says folowing:
>>it is safe to assume IEEE-754 in most portable code these days
> https://www.gnu.org/software/autoconf/manual/autoconf.html#Floating-Point-Portability
Personally I wouldn't be very happy about an IEEE754 assumption. I did
go to the trouble of testing Postgres on a VAX and we fixed the few
instances where it had such dependencies for a net gain. If we
intentionally put a dependency in in one place then we'll never be
able to determine anywhere else where there are unintentional
dependencies.
I haven't followed the thread closely but I'm puzzled why you would
need to use bit twiddling to set a floating point number. Isn't there
a perfectly good way to calculate the value you want using ldexp() and
other standard C library functions?
--
greg
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