Re: 2.9.11?

[Daniel J Sebald]

John W. Eaton wrote:
> On 19-Apr-2007, Daniel J Sebald wrote:
>
> | Daniel J Sebald wrote:
> | 
> | > The only other unusual results are the scripts/elfun/acscd.m and asecd.m 
> | > tests with the division by zero problem that hangs.
>
> So it is the function asecd.m and acscd.m that have problems?  Then I
> would thing that it is really asin and acos that have problems because
> the others are just .m files.

Right.  We traced this to asin(inf) and acos(inf), which should be undefined.


> Look in src/mappers.cc.  There you'll find
>
>   DEFUN_MAPPER (asin, 0, 0, 0, asin, 0, asin, -1.0, 1.0, 0, 1,
>     "-*- texinfo -*-\n\
> @deftypefn {Mapping Function} {} asin (@var{x})\n\
> Compute the inverse sine of each element of @var{x}.\n\
> @end deftypefn");
>
> So along with the comments in defun.h where DEFUN_MAPPER is defined,

Saw those...


> this means that there are two versions of asin defined:
>
> //   d_d_map is a pointer to a function that should be called for real
> //     arguments that are expected to create real results.
> //
> //   c_c_map is a pointer to a function that should be called for
> //     complex arguments that are expected to create complex results.
>
> The complex versions of asin and acos come from
> liboctave/lo-mappers.cc.  Their definitions are:
>
>   Complex
>   acosh (const Complex& x)
>   {
>     return log (x + sqrt (x*x - 1.0));
>   }
>
>   Complex
>   asin (const Complex& x)
>   {
>     static Complex i (0, 1);
>
>     return -i * log (i*x + sqrt (1.0 - x*x));
>   }

Ah, there it is.  Thanks...

Well, it seems the sqrt() routine may be where things are hanging:

octave:1> i*Inf
ans = NaN + Infi
octave:2> log(i*Inf)
ans = NaN - NaNi
octave:3> log(Inf)
ans = Inf
octave:4> sqrt(1.0 - Inf*Inf)
Press Control-C again to abort.
panic: Interrupt -- stopping myself...
attempting to save variables to `octave-core'...
save to `octave-core' complete

address@hidden ~]$ octave
octave:1> sqrt(-Inf*Inf)
Press Control-C again to abort.
panic: Interrupt -- stopping myself...
attempting to save variables to `octave-core'...
save to `octave-core' complete

address@hidden ~]$ octave
octave:1> sqrt(Inf)
ans = Inf
octave:2> sqrt(-3)
ans =  0.00000 + 1.73205i
octave:3> sqrt(-Inf)
Press Control-C again to abort.
panic: Interrupt -- stopping myself...
attempting to save variables to `octave-core'...
save to `octave-core' complete

So, it looks like the failing case is sqrt(-Inf).  OK, now where is the complex 
version of square root, std::sqrt?  :-)

Dan