From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
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To: | Shachar Shemesh <shachar(at)shemesh(dot)biz> |
Cc: | Peter Eisentraut <peter_e(at)gmx(dot)net>, pgsql-hackers(at)postgresql(dot)org, Greg Smith <gsmith(at)gregsmith(dot)com>, oledb-devel(at)pgfoundry(dot)org |
Subject: | Re: Re: [Oledb-dev] double precision error with pg linux server, but not with windows pg server |
Date: | 2007-05-23 14:11:56 |
Message-ID: | 20121.1179929516@sss.pgh.pa.us |
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Shachar Shemesh <shachar(at)shemesh(dot)biz> writes:
> Before you explode at me (again :), I'm not arguing that you can do
> binary based calculations of decimal numbers without having rounding
> errors that come to bite you. I know you can't. What I'm saying is that
> we have two cases to consider. In one of them the above is irrelevant,
> and in the other I'm not so sure it's true.
You're setting up a straw-man argument, though. The real-world problem
cases here are not decimal, they are non-IEEE binary floating
arithmetic. The typical difference from IEEE is slightly different
tradeoffs in number of mantissa bits vs number of exponent bits within a
32- or 64-bit value. I seem to recall also that there are machines that
treat the exponent as power-of-16 not power-of-2. So depending on which
way the tradeoffs went, the other format will have either more precision
or more range than IEEE.
regards, tom lane
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