[Numpy-discussion] Slightly off-topic - accuracy of C exp function?

[Pauli Virtanen]

Hi,

27.04.2014 01:37, Matthew Brett kirjoitti:
[clip]
> Take-home : exp implementation for mingw-w64 is exactly (floating
> point) correct 82% of the time, and one unit-at-the-last-place off for
> the rest [1].  OSX is off by 1 ULP only 0.2% of the time.
> 
> Is mingw-w64 accurate enough?  Do we have any policy on this?

I think as mentioned, the C standards don't specify accuracy
requirements. Errors of a couple of ULP should be still acceptable.

Re: powell test --- if this turns out to be complicated to deal with,
just go ahead and disable the trace test.

Optimization routines contain statements of the form `if a > b: ...`
with floating point numbers, so that the execution path can be sensitive
to rounding error if you're unlucky, and the chances go up as the
iteration count increases.

-- 
Pauli Virtanen