Hi Guido,
mhh... that was my gut feeling when reading the assign documentation. So
it basically does not really do a search for solutions but just assigns
the (first) variable, does propagation, continues with the remaining
variables until all are assign or no solution is found...
no, that's not what I need. True enough.
So either I do the external handling as Christian suggested, ie.
something like
//////////////////////////////////////
CSP p = new CSP();
// branch on A
branch(p, p.A, INT_VAR_SIZE_MIN, INT_VAL_MIN);
Gecode::DFS<CSP> dfsA(p);
delete p;
// get all solutions for valid A assignments
while ( CSP solA = dfsA.next() ) {
// branch on B
branch( solA, solA.B, INT_VAR_SIZE_MIN, INT_VAL_MIN);
Gecode::DFS<CSP> dfsB(solA);
// get first solution for B assignment
if( CSP solAB = dfsB.next() ) {
cout <<"overall solution = " <<solAB <<endl;
delete solAB;
}
delete solA;
}
//////////////////////////////////////
or I am back to my first guess, ie. I have to write my own branching
that stops after the first solution on B to fall back to the branching
on A...
:/ what a pitty. :) Was hopeing on something hidden in the space (as
the branching) without much work.
But thanks for your thoughts. Helped a lot to clearify the problem.
So long,
Martin
Am 28.01.2013 22:55, schrieb Guido Tack:
Hi guys,
just using assign after branching on A doesn't work. Assign has a very
different semantics, you can only use it if you are guaranteed to find a
solution using the leftmost branch.
What you need here is either the two-stage search Christian mentioned: for every solution
to A, run a new search engine that finds a single solution for the rest of the variables.
Or implement something like the "once" combinator. I think our radiotherapy
example includes code for this.
We can't provide a generic solution very easily, because it's a combinator that modifies
another search heuristic (so it would have to be "wrapped around" the existing
branchers).
Cheers,
Guido
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