Re: Use of C99 extra long double math functions after r236148

On Fri, Jul 13, 2012 at 09:41:00PM +1000, Peter Jeremy wrote:
> On 2012-Jul-11 15:32:47 -0700, Steve Kargl <sgk_at_troutmask.apl.washington.edu> wrote:
> >I know an approach to implementing many of the missing
> >functions.
> 
> Are you willing to share this insight so someone else could do the work?

For the missing trig and hyperbolic functions of complex float
and complex double arguments, one can follow the approach in
msun/src/s_ccosh[f].c.  For the missing hyperbolic functions
of long double and complex long double argument, people will
need to wait for expl() and expm1l() to show up in tree.  I
have a working expl() and almost working expm1l() for ld80
systems.  Until a few months ago, I did not have access to a
ld128 system, so I haven't wasted my time implementing ld128
version that I could not test.

> >When I do find
> >some free time, I look at what is missing and start to
> >put together a new function.  At the moment, it seems
> >that it takes 3+ years to get a new function written,
> >tested, and committed.
> 
> And, from what I can see, much of this is done quietly - which opens
> up the possibility that two people might both implement the same code
> or that people will avoid the area in fear of treading on someone
> else's toes.  As I said previously, I believe the existing wiki page
> could be improved to form a central co-ordinating point to show what
> what activity is (or isn't) occurring.

Well, I've posted the code I've written to freebsd-standards
mailinglist more than once, and have only ever received comments
from exactly 2 people.    

> >but most people seem to push the "easy button" and want
> >to grab either cephes or netlib's libm.  There are
> >technical issues with this approach that I won't 
> >rehash again.
> 
> Doing it properly requires significant effort by people with fairly
> specialised skills.  Whilst the project has several people with the
> skills, it appears that none of them currently have the time.  In the
> meantime, FreeBSD is taking free kicks from other FOSS groups that
> have gone down the quick-and-dirty path.
> 
> AFAIK, none of the relevant standards (POSIX, IEEE754) have any
> precision requirements for functions other than +-*/ and sqrt() - all
> of which we have correctly implemented.  I therefore believe that, for
> the remaining missing functions, the Project would be best served by
> committing the best code that is currently available under a suitable
> license and cleaning it up over time (as was done for the current
> libm).

Well, hopefully, the someone who takes the best available code
also tests this code before it is committed.  I suspect that 
some if not all of those codes that involve complex arguments
will have problems with the requirements in n1256.pdf[1], because
neither gcc in base nor clang do complex arithmetic correctly
under certains conditions when an expression uses I from complex.h.

[1] http://www.open-std.org/jtc1/sc22/wg14/www/docs/n1256.pdf

-- 
Steve