[gecode-users] Float overflow exceptions with 'linear' in 6.0.1

[Christian Schulte]

Hi,

This is not a bug: it is really a restriction compared to Gecode 5. You will have to do some thinking on the initial variable domains.

The implementation in Gecode 5 _was_ in fact broken: the overflow might not have occurred but the new checks make sure that there will never be an overflow.

Cheers
Christian

--
Christian Schulte, https://chschulte.github.io/
Professor of Computer Science
Software and  Computer Systems
School of Electrical Engineering and Computer Science
KTH Royal Institute of Technology, Sweden

From: users-bounces at gecode.org <users-bounces at gecode.org> On Behalf Of Konvicka Filip
Sent: 24 August 2018 09:48
To: 'users at gecode.org' <users at gecode.org>
Subject: [gecode-users] Float overflow exceptions with 'linear' in 6.0.1

Hi,

I'm in process of upgrading our code to Gecode 6.0.1 (which looks great by the way!)

I found some cases where code that used to run fine with Gecode 5 now throws exceptions.  The following is a simple example that demonstrates this.  I was able to work around to defaulting to (Gecode::Float::Limits::max/4) as the default max bound of float variables, but I think it's still probably a bug.

Thanks,
Filip

#include <gecode/float.hh>
#include <iostream>
using namespace Gecode;
int main() {
  struct MySpace : public Space {
    Space* copy() { return nullptr;  }
  };
  MySpace s;

  try {
    FloatVarArgs args(2);
    args[0] = FloatVar(s, 0., Gecode::Float::Limits::max);
    args[1] = FloatVar(s, 0., Gecode::Float::Limits::max);
    FloatVar result(s, 0., Gecode::Float::Limits::max);
    linear(s, args, FRT_EQ, result);
  }
  catch (std::exception& e) {
    std::cerr << e.what() << "\n";
  }

  try {
    FloatVarArgs args(2);
    args[0] = FloatVar(s, 1., 1.);
    args[1] = FloatVar(s, 0., Gecode::Float::Limits::max);
    FloatVar result(s, 0., Gecode::Float::Limits::max);
    linear(s, args, FRT_EQ, result);
  }
  catch (std::exception& e) {
    std::cerr << e.what() << "\n";
  }
}
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://www.gecode.org/pipermail/users/attachments/20180828/252a2379/attachment-0001.html>