[gecode-users] Limits on nonlinear constraints

[Michael Mac-Vicar]

Javier,

I didn't try but I'd check the operators used in the last constraint.

Best,
Michael Mac-Vicar

On Aug 20, 2010 8:45 AM, "Javier Romero" <libicocco at gmail.com> wrote:
> Hi,
> I'm a newbie in Gecode, but in the first stages of trying it i've found
> something that puzzles me. After writing a program with a set of highly
> nonlinear constraints which includes the following constraint (apart from
> others)
>
> IntVar k = expr(*this, 2*x0*x1*x2);
> IntVar kc01= (*this,x2*(sqr(x0)+sqr(x1)-sqr(d01min)));
> IntVar kc02= (*this,x1*(sqr(x0)+sqr(x2)-sqr(d02min)));
> IntVar kc12= (*this,x0*(sqr(x2)+sqr(x1)-sqr(d12min)));
> rel(*this,k*(sqr(kc01)+sqr(kc02)+sqr(kc12)) < (k*k*k+2*kc01*kc02*kc12));
>
> i get an output like this:
>
> Initial
> propagators: 0
> branchers: 0
>
> Summary
> runtime: 0.000 (0.174000 ms)
> solutions: 0
> propagations: 0
> nodes: 0
> failures: 1
> peak depth: 0
> peak memory: 18 KB
> That is, it returns inmediately with no solution. However, the problem has
a
> solution, and actually it finds it by commenting the last lined of the
code
> posted above (by chance; the constraint is actually necessary). This is
how
> the output looks when the solution is found:
> Initial
> propagators: 82
> branchers: 1
>
> Summary
> runtime: 54.402 (54402.259000 ms)
> solutions: 1
> propagations: 638013328
> nodes: 1237660
> failures: 618828
> peak depth: 414
> peak memory: 122 KB
>
> I tested manually (and with a python script) that the solution obtained is
> compliant with the constraint that was removed. So i wonder if there is a
> limitation on the level of the nonlinearities in Gecode (i think it's
> unlikely), in the number of constraints (also unlikely) or what else could
> have happened. The code is basically an adaptation of SMM example to my
> arithmetic constraints. I can post it if necessary.
>
> Best regards,
> -- Javier Romero --
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://www.gecode.org/pipermail/users/attachments/20100820/9adbb915/attachment.htm>