From: Philipp Marcus <marcus_at_...247...>

Date: Wed, 28 Apr 2010 09:25:44 +0200

Date: Wed, 28 Apr 2010 09:25:44 +0200

Hi, thanks for your hints. In my case the problem is, that inside the mycon(..,Y,1) predicate there exists a ic_sets:in(X,Y,B) predicate (so Y is a set variable). When I call mycon(..,Y,1) by my self, the the domain of the set is correctly reduced. But calling mycon_constr(..,Y,1) (which should immediatle 'delegate' to the mycon(..,Y,1) predicate, as B is instantiated) does not reduce the domain of the set. mycon_constr(..,Y,B) :- mycon(..,Y,B) infers most. I don't know exactly but I might guess that this has something to do with ic_sets and a missing msg predicate. So my question was: Given the predicate mycon(..,Y,1) :- ... and mycon(..,Y,0) :- ... is there a general pattern to combine the two to a reified constraint without using propia? Especially I'd like to know how you would check the entailment or disentailment when B is unknown. For the two cases, where B is instantiated I'd implement the predicate something like this: mycon_constr(..,Y,B) :- (ground(B)-> mycon(..,Y,B); suspend( mycon_constr(..,Y,B), 3, [B] -> inst)). But I need to include the entailment/disentailment check. I'd be really happy if somebody could give me a suggestion. Best regards, Philipp Am 28.04.2010 02:31, schrieb Joachim Schimpf: > Philipp Marcus wrote: > >> Hi, >> >> I wanted to write a custom reified constraint and already created the >> mycon(...,1) and the mycon(...,0) version. Then I wanted to combine them >> with propia to say mycon_constr(...,B) :- >> mycon(...,B) infers most. >> >> But now I have the following problem: >> calling mycon_constr(...,1) gives me less propagation than calling >> mycon(...,1). But in my opinion it should reduce the variable bounds to >> the same intervals (I'm using ic). >> > Using infers/2 only makes sense when you apply it to a nondeterministic > (i.e. more than one solution) predicate. For example the following > gives you 3 solutions: > > ?- member(X, [1, 2, 3]). > X = 1 > Yes (0.00s cpu, solution 1, maybe more) > X = 2 > Yes (0.00s cpu, solution 2, maybe more) > X = 3 > Yes (0.00s cpu, solution 3) > > and by wrapping this in infers/2 you get a single solution which is > the "convex hull" of the alternative solutions: > > ?- member(X, [1, 2, 3]) infers ic. > X = X{1 .. 3} > Yes (0.00s cpu) > > Only in the latter case do we talk about "propagation". > If you have the impression that your unannotated predicate gives > your more "propagation", then you may have overlooked that you get > alternative solutions that need to be taken into account as well. > > > >> Now I thought of doing the reified stuff by my self, instead of using >> propia in order to circumvent the problem. So I wanted to ask if there >> is general pattern that fulfills the requirements for the three situations: >> >> * Reified variable is unbound (check if constraint is entailed) >> > You also want to check if the constraint is disentailed (i.e. whether > you can bind the Boolean to 0). > > >> * Reified variable is bound to 0 >> * Reified variable is bound to 1 >> >> Especially I'd like to know how to realize the first case best. Would >> you use suspend to do that? And how would you do that? >> > The implementation of a reified constraint is not really any different > from any other constraint - you just have an extra argument. > For example, if your original constraint has the following truth table: > > and(0,0,0). > and(0,1,0). > and(1,0,0). > and(1,1,1). > > then the reified version has this one > > and_reif(0,0,0,1). % the entailed cases > and_reif(0,1,0,1). > and_reif(1,0,0,1). > and_reif(1,1,1,1). > and_reif(0,0,1,0). % the disentailed cases > and_reif(0,1,1,0). > and_reif(1,0,1,0). > and_reif(1,1,0,0). > > and you can make either into a constraint by using infers/2, e.g. > > ?- and_reif(0, Y, 1, B) infers ic. > Y = Y{[0, 1]} > B = 0 > Yes (0.00s cpu) > > > For an example of direct implementation without propia, look at the library > source file sd.ecl, which implements a reified predicate (&\=)/3. > > > -- Joachim > > ------------------------------------------------------------------------------ > _______________________________________________ > ECLiPSe-CLP-Users mailing list > ECLiPSe-CLP-Users_at_lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/eclipse-clp-users >Received on Wed Apr 28 2010 - 07:25:51 CEST

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