[SciPy-dev] Bessel functions from Boost

[Pauli Virtanen]

Sun, 08 Feb 2009 20:25:37 -0800, Michael Abshoff wrote:
> David Cournapeau wrote:
>> This is much better - I really don't see the point of using C++ for
>> math functions. I am ok with this.
> 
> Out of curiosity: I checked the boost website and it states for the math
> lib:
> 
> "All the implementations are fully generic and support the use of
> arbitrary "real-number" types, although they are optimised for use with
> types with known-about significand (or mantissa) sizes: typically float,
> double or long double."
> 
> Since I assume some people around here are interested in arbitrary
> precisions and after looking some more at the documentation it seems
> that that library only supports this via using an NTL type which in turn
> uses GMP. NTL itself is GPLed, GMP is LGPL, so either one does not fit
> the licensing requirements of Scipy.

Yeh, arbitrary precision could be nice in principle.

But as I see it, at the moment it's out-of-scope for Scipy. Right now, we 
only need good implementations in double precision. These we can get for 
some functions for example by adapting the Boost code (and re-testing it) 
-- this is much less work than rewriting everything from scratch.

> David mentioned to write a library from scratch and I also assume that
> you want arbitrary precisions. Given that GMP is LGPL, the arbitrary
> precisions code in OpenSSL is covered by a BSD advertising clause (which
> might or might not be a deal breaker around here) what do you suggest to
> do about arbitrary precisions? I am not aware of any BSD 2 or 3 clause
> license library besides mpmath :)

For the present, I'd say that we should leave the arbitrary-precision 
functions implemented in mpmath.

-- 
Pauli Virtanen