I'd suggesting checking out sigaddset, and the SIGFPE signal.
Install your own signal handler and do whatever you want when you
detect a SIGFPE. I believe SIGFPE includes underflow, overflow, and
divide by zero, not sure though.
On Mon, Mar 12, 2001 at 10:08:37AM -0800, Peter Jay Salzman wrote:
> dear all,
>
> i have code which looks like:
>
> long double dr;
> long double dt;
> long double rend;
> long double ratio;
> long int N;
> long unsigned int max_tstep;
>
> ratio = 2.0L;
> N = 800;
> dr = rend / ((long double)N - 1.0L);
> dt = ratio*pow(dr, 2.0L);
>
> max_tstep = (long unsigned int) ceil(endtime / dt);
>
> sometimes ceil(endtime / dt) is very large, like 2.10944e+85. this is too
> large even for a long long int. max_tstep overflows.
>
> sometimes i don't catch the overflow, and my program can run for a long
> time, producing garbage.
>
> is there some kind of flag that i can check that gets raised when a
> calculation overflows? i have many such calculations (which are performed
> once at the beginning, so i'm not worried about performance penalty).
>
> i guess i can take a look at limit.h to and compare the maximum long
> unsigned int to the value of endtime / dt, but i'd prefer a different
> solution if one exists. surely there's got to be SOME way of detecting this
> kind of error?
>
> i care not for portability. it's running on a bunch of pentium II, III and
> athlon class machines and nothing else. gcc extensions are welcome
> (although i took a look and didn't see anything immediately helpful).
>
> the problem is fairly pernicious. normally i would rescale variables, but
> for this particular problem, a rescaling simply shifts the problem from one
> variable to another.
>
> thanks!
> pete
>
> --
> "Coffee... I've conquered the Borg on coffee!" [EMAIL PROTECTED]
> -- Kathryn Janeway on the virtues of coffee www.dirac.org/p
