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Re: [GCC 4.2 Project] Omega data dependence test
On Tue, Aug 09, 2005 at 04:59:28PM +0200, Sebastian Pop wrote:
> Joe Buck wrote:
> > Algorithms that are sometimes exponential can still be used if there is
> > a cutoff mechanism, to abort the algorithm if it exceeds a budget. This
> > assumes that we can then fall back to an algorithm that might produce
> > inferior results, but will produce something usable in reasonable time.
> >
>
> Okay, I stand corrected. As a practical implementation we can have a
> mechanism as push/pop timevar, that would monitor the time and space
> of an algorithm and that can cancel the computation for failing on a
> safe approximation. As a first concretization, I was thinking to use
> threads, but I'm not sure whether this is suitable for GCC.
The problem with using time as a cutoff is that you then get results that
can't be reproduced reliably. Better to count something that is a feature
of the algorithm, e.g. number of executions of some inner loop, number of
nodes visited, or the like, so that all users get the same results.