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 interest! > [...] > 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 over http://lyre.mit.edu/~powell/petscgraphics.html? > Share and enjoy, thanks in advance for any help you can provide. Thanks for your insight, scr
