Python -- floating point arithmetic

[Stefan Krah]

Adam Skutt <askutt at gmail.com> wrote:
> > > I actually agree with much of what you've said.  It was just the
> > "impossible" claim that went over the top (IMO).  The MPFR library
> > amply demonstrates that computing many transcendental functions to
> > arbitrary precision, with correctly rounded results, is indeed
> > possible.
> That's because you're latching onto that word instead of the whole
> sentence in context and making a much bigger deal out of than is
> appropriate.  The fact that I may not be able to complete a given
> calculation for an arbitrary precision is not something that can be
> ignored.  It's the same notional problem with arbitrary-precision
> integers: is it better to run out of memory or overflow the
> calculation?  The answer, of course, is a trick question.

In the paper describing his strategy for correct rounding Ziv gives an
estimate for abnormal cases, which is very low.

This whole argument is a misunderstanding. Mark and I argue that correct
rounding is quite feasible in practice, you argue that you want guaranteed
execution times and memory usage. This is clear now, but was not so apparent
in the "impossible" paragraph that Mark responded to.


I think asking for strictly bounded resource usage is reasonable. In cdecimal
there is a switch to turn off correct rounding for exp() and log().



Stefan Krah