Re: problem with output of the program on different OS

On May 13, 4:46=A0am, Ben Bacarisse <ben.use...@[EMAIL PROTECTED]
> wrote:
> Bart <b...@[EMAIL PROTECTED]
> writes:
> > On May 13, 1:39=A0am, Ben Bacarisse <ben.use...@[EMAIL PROTECTED]
> wrote:
> >> Bart <b...@[EMAIL PROTECTED]
> writes:
> >> > On May 12, 6:27=A0pm, pereges <Brol...@[EMAIL PROTECTED]
> wrote:

> > I would expect the answer to be wrong by one bit or so. My gcc/3.4.5
> > gives -5e-16.
>
> Mine is 4.2.3. =A0The point is I think 0 is a correct and permitted
> answer. =A0It is not at all strange (to me).
>
> This has got so surreal that I have just downloaded Pelles C. =A0If I
> leave the bug in I get this output:
>
> Es: inf Ei: 1.112194e-04 RCS: inf

I was also getting these weird results. I independently made the
initialisation change and got the results of 7.39... except for Pelles
which gave 7.08...;

>
> If I correct it by setting the missing parts of the complex numbers to
> 0 I get this:
>
> Es: 7.391785e-11 Ei: 1.112194e-04 RCS: 8.351773e+00
>
> which is exactly what gcc 4.2.3 and lcc-win32 give me. =A0It seems to be
> a bug of the most ordinary nature.

My Pelles and the OP's gave 7.08....

In fact my Pelles was an old V2.9, I just downloaded the new version
and it gave the same results, namely 7.08.

> > I was intrigued in why 1 compiler out of 4 gave a different result,
> > and tracked it down to this behaviour
>
> I am far from sure that you have. =A0Does the version you traced have
> uninitialised data and does the problem remain when you add the two
> extra zero initialisations? =A0If, so I will agree it looks odd, but so
> far it seems to be a common all-garden bug in the code.

There's lots of other uninitialised data which may or may not be
affecting anything else. However the 7.08/7.39 discrepancy *was*
traced to these zero/near zero values.

But I've now changed a couple of things: < 0.0 to < (-EPSILON) and >
1.0 to > (1+EPSILON).

*Now*, all my 4 compilers (5 including new Pelles) give the 7.08...
result.

(Whether that is right or not, I've still no idea.)


--
Bartc