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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