|Re: [eigen] (General question) Floating point: why are 'inf' and 'nan' slow?|
[ Thread Index |
| More lists.tuxfamily.org/eigen Archives
Benoit Jacob a écrit :
> Sorry for adding to the currently already high traffic here.
> Here, on linux / x86, my programs run 100x slower when the
> floating-point values are 'inf' or 'nan'.
> Only scalar code is affected, SSE code is not affected.
> I haven't enabled floating-point exception signals. I don't have a FP
> signal handler. Just any basic c++ program.
> Can this be "fixed"? How?
> Otherwise, I really need to make sure that solve() methods avoid
> producing such special values when no solution exists --- otherwise
> they take much longer to return.
> Thanks for your help,
may be *before* arriving to those extremes you've encountered
"denormalized numbers" ?
There are provisions to get rid of them with SSE, while in regular "387"
code you must explicitly deal with them. This is consistent with your
observation (but it's not a proof).
4 chemin de Malacher
38240 Meylan - France
Tel: +33 438 020 555
Fax: +33 438 020 525