cvs commit: src/lib/msun/src e_expf.c

[Alexander Leidinger]

David Schultz <das at freebsd.org> wrote:

> This is related to a good reason why we can't switch the default
> precision on i386 to extended.  Many of the functions in libm use
> minimax approximations, which are ``optimal'' approximations in
> the sense that their maximum error over all in-range inputs is the
> smallest possible (unless more terms are used).  These approximations
> take rounding error into account, so when the machine precision is
> increased, they're no longer optimal and the error in the approximation
> can increase significantly.  There are less efficient methods that
> don't depend on the exact machine precision, e.g. Chebyshev
> approximations, but it would be a PITA to switch everything.

What's the problem with recomputing the minimax approximations for extended
precision? Is there no tool available to compute them so it is more work
than you are willing/able to do ATM? Or is it the amount of computing time
needed to recompute the approximations?

Bye,
Alexander.

-- 
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