[Axiom-developer] Re: differences

[gdr]

Quoting address@hidden:

> As far as I know so far Axiom just uses the underlying lisp values
> from cos and acos.
>
> I don't consider it a bug but I don't consider it "stable" either.
> All other values of all other functions seem to give the same
> result and that result matches the input in this case. It's a
> curious result though. I'd expect that they are using Chebyshev
> polynomials and I'd have expected a symmetric result. Somebody
> clearly "optimized" the world by saving an instruction somewhere.

Note also that in GCC-4.3, the compiler will be constant-folding
"non-trivial" functions called with constant arguments, e.g. sin(9.3),
thanks to MPFR and all that.  Consequently, the test must be precise
about what it is testing and how to reproduce the results across
platforms, otherwise we could just remove it.

> The problem arose trying to explain a failing case in the
> regression tests. Now that I understand it better it's not an issue.
>
> Tim