Follow up: The behavior is correct for real argument:
In [20]: sinh(1000) Out[20]: inf In [21]: cosh(1000) Out[21]: inf In [22]: tanh(1000) Out[22]: 1.0 So maybe we should look there for good logic, Mark On Fri, Jan 28, 2011 at 11:45 AM, Mark Bakker <mark...@gmail.com> wrote: > Good point, so we need a better solution that fixes all cases > > > >> I'll file a ticket. > >> > >> Incidentally, if tanh(z) is simply programmed as > >> > >> (1.0 - exp(-2.0*z)) / (1.0 + exp(-2.0*z)) > > >This will overflow as z -> -\infty. The solution is probably to use a > >different expression for Re(z) < 0, and to check how other libraries do > >this in case the above still misses something. > > > > > Pauli > >
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