Re: problem with output of the program on different OS

On May 12, 8:06 pm, Bart <b...@[EMAIL PROTECTED]
> wrote:

> I had a further look at Pelles C version (now that I can run it from
> the command line, I can make progress..)
>
> With 3 compilers, ray 463 hits only triangle 654 of the 1200
> triangles.
> With Pelles C, ray 463 hits triangles 654 and 745, at equal distances.


I just added a raycount member to ray data structure and kept track of
rays hitting triangles. I got some what different results. ray 463 is
hitting triangle 943 at distance 1006.67112

a ray hitting two triangles at same distance is nothing but  ray
hitting the edge shared by two triangles or the vertex.

> Varying your EPSILON made no difference.

Well I  varied EPSILON and there was a little difference in output but
still no where near the results obtained with other compilers.

> So it starts to look more like some strange numeric problem; perhaps
> Pelles C does some calculations a little differently, or perhaps
> something more serious; this requires more investigation by someone
> with a lot more time!

> It could still be a bug in /your/ calculations which may depend too
> heavily on some very small value which is treated differently between
> different C systems.

maybe you are right but isn't it strange that PellesC is the only
compiler giving a result like this. If there was a serious bug in the
program, then there would have been atleast one compiler which could
have given strange result ?


> BTW this is a hell of a complicated program; I wouldn't have used C
> for this. Not until it was 100% working with some reference results
> anyway. (I(/we?) still don't know what the right output is supposed to
> be. Makes testing a little difficult!)


What other languages in your opinion could have been used ? I was told
C because speed was im****tant to my application.