[gecode-users] Symmetries, activity branching, and graph coloring

[Stefano Gualandi]

Hi,
the new Lightweight Dynamic Symmetry Breaking could be used also for the graph coloring
example, since the color values are symmetric, right?

Something like (referring to gecode/example/graph-color.cpp)

    Symmetries syms;
    syms << ValueSymmetry(IntArgs::create(g.n_v,0));
    […]
    branch(*this, v, INT_VAR_SIZE_MIN(), INT_VAL_MIN(), syms);

If the answer is "no", forget about the remaining of this email  :-)



If the answer is "yes", then there is something wrong when using symmetry breaking together
with an activity based branching as:

	branch(*this, v, INT_VAR_ACTIVITY_SIZE_MAX(opt.decay()), INT_VAL_MIN(), sums);

Since the example gives "seg fault". I have tried all the variable selection strategies,
but only those based on the "activity" have this issue.

You can find attached a modified graph-color.cpp example that exposes the problem
(with an additional option for the activity-based branching):

./examples/graph-color -branching sizeact

Thanks in advance,
cheers,
Stefano

-------------- next part --------------
A non-text attachment was scrubbed...
Name: graph-color.cpp
Type: application/octet-stream
Size: 19271 bytes
Desc: not available
URL: <http://www.gecode.org/pipermail/users/attachments/20130515/4eec97aa/attachment.obj>