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Re: [Axiom-developer] differences

From: Gabriel Dos Reis
Subject: Re: [Axiom-developer] differences
Date: 01 Apr 2007 22:43:06 -0500

address@hidden writes:

| Ok, the problem isn't in axiom and it appears that it isn't in GCL.
| I built the same GCL sources (no axiom) on redhat 9 and fedora 5.
| The result of
| (cos (acos 0.7)) on Redhat is 0.69999999999....96
| (cos (acos 0.7)) on Fedora is 0.70000000000...07
| so the problem change is likely somewhere in a system library
| that gets linked into GCL. Since every other combination of
| sins, cos, logs, exps, etc ends up with 0.69999.... I have
| to conclude that there is a very minor bug in the Fedora lib.
| Anybody happen to know in which system library cos/acos lives?

C mathematical functions are part of the C standard library.  Some
systems put them in a separate library libm.{a,so} -- GNU/Linux sytems
come with glibc.  Other systems don't make a dictintion -- because the
C standard does not make one.

Furthermore, as I dicussed a few days ago, you're going to be at the
mercy of systems if you insist on using 'long-float -- it is not
always efficient and you can't predice the accuracy across platforms.
Use 'double-float.

-- Gaby

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