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List: kde-devel
Subject: Re: dump question
From: "Dirk A. Mueller" <dmuell () gmx ! net>
Date: 1999-08-08 15:17:25
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Uwe Thiem <uwe@uwix.alt.na> wrote:
> Sure, if the small numbers get much smaller this problem will occur
> eventually. But why so early? At this stage the sums should
> differ but don't. #-(
Only the first 12 decimal digits are significant when you use double's
under bad conditions, 14 under good conditions.
Some platforms might map double to float, which only has 5-7
significant decimal digits, therefore it might be even worse.
You have to change your algorithm so that there are at most 5-6
significant digits guaranteed.
remember: not the absolute value count, but the relative significance,
i.e.
1000000000000000000000000.0 + 0.1 won't work, but
1.0 + 0.1 will do.
Under most cases the solution is a fixed point integer, which is
accurate enough for almost everything.
--
Dirk A. Mueller
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