Re: Correct way to build .deb with -mieee
Adam C Powell IV wrote:
> Of course, if it's possible to avoid divides by zero without performance
> penalty, I would love to.
Yep, that would be something I'd love, too. The only way I know
of (generally spoken) is to move such tests for potential divisions
by zero *as far as possible* out of the innermost loops of an impl
of performance critical loops (but do such tests, somewhere).
Well, if possible.
> The offending code [...]
Thanks for posting this, without your excpicit hint most likely I
never noticed what PETScGraphics is (or does). And (of course) I
must admit, that I do not understand your sources fully without
even having used (or debugged) your program. But you catched my
> I could trap for these conditions with an if statement around them, but
> wouldn't that slow things down?
Might be true.
> Note that it is possible to have one of
> these three divisions by zero and still produce a triangle or two; one
> can even have C1=C2<q and C0=C3>q and get two triangles, so we can't
> just test for any zeroes and skip the whole thing. It just seems easier
> to do it this way, and because it's just for graphics, I don't really
> care about the divide by zero.
In this case (and without deeper knowlegde), I would say
"go with -mieee" (for that specific function).
> I don't know whether this algorithm is optimal, nor whether my
> implementation can be improved, just that it worked right the first
> time, with lots and lots of code in DrawTetWithPlane(), and I haven't
> touched it since. If you have the interest and time to try to lose the
> SIGFPE without -mieee, or even speed things up, feel free to apt-get
> source petscgraphics and look at petscgraphics.c.
As I told before, you catched my interest. Should I prefer apt-get
> Share and enjoy, thanks in advance for any help you can provide.
Thanks for your insight,