Alejandro Arbelaez wrote:
Right now, I'm working on a heuristic using Gecode, and I need to
record some information during the propagation process.
So far things are going well, but now I'm facing a problem with re-
writable propagators because sometimes there is call to
GECODE_REWRITE which (if I understand well), removes the current
propagator from the space and impose another one,
Exactly.
but in (http://www.gecode.org/gecode-doc-latest/int_2element_2view_8icc-source.html#l00537
) [ViewDom<VA,VB,VC>::propagate -- line 537] there is an explicit
imposition of DomEq (i.e. dispose the current propagator and
creates the new one.), please let me know, whether these two things
are the same or not.
They are essentially the same - have a look at the definition of
GECODE_REWRITE at
http://www.gecode.org/gecode-doc-latest/macros_8icc-source.html#l00115
The reason why we explicitly create the new propagator and then
subsume the old one here is how Rel::EqDom::post works:
http://www.gecode.org/gecode-doc-latest/int_2rel_2eq_8icc-source.html#l00142
It first checks for assignment, and then checks that the arguments are
not the same, and only then posts the propagator. But in the element
case, we already know that none of the variables is assigned and
they're not the same, so we want to avoid the checks. And the
GECODE_REWRITE macro cannot cope with propagators created via new, it
requires them to be created by a post function.
I hope this clarifies things!
Cheers,
Guido
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