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Re: [PPL-devel] More floating point problems on the Alpha
- From: Joe Buck <Joe dot Buck at synopsys dot COM>
- To: Abramo Bagnara <abramobagnara at tin dot it>
- Cc: Roberto Bagnara <bagnara at cs dot unipr dot it>, gcc at gcc dot gnu dot org, "The Parma Polyhedra Library developers' list" <ppl-devel at cs dot unipr dot it>
- Date: Mon, 22 Sep 2008 13:50:21 -0700
- Subject: Re: [PPL-devel] More floating point problems on the Alpha
- References: <48D7DBAE.6000704@cs.unipr.it> <48D7F86E.1080106@tin.it>
On Mon, Sep 22, 2008 at 09:56:30PM +0200, Abramo Bagnara wrote:
> The problem come from the fact that for astonishing reasons 1.4e-45f is
> not seen as 1.4e-45.
Why is this astonishing? The smallest positive single-precision IEEE
floating point number is roughly 1.175494e-38. Since user-specified
numbers are rounded to the closest representable value, 1.4e-45f is
a fancy way of typing zero.
Double-precision values have much greater dynamic range; DBL_MIN is roughly
2.225074e-308.