/* $Id$ Part of SWI-Prolog Author: Markus Triska E-mail: triska@gmx.at WWW: http://www.swi-prolog.org Copyright (C): 2005, Markus Triska This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version. This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU Lesser General Public License along with this library; if not, write to the Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA As a special exception, if you link this library with other files, compiled with a Free Software compiler, to produce an executable, this library does not by itself cause the resulting executable to be covered by the GNU General Public License. This exception does not however invalidate any other reasons why the executable file might be covered by the GNU General Public License. */ :- module(clp_distinct, [ vars_in/2, vars_in/3, all_distinct/1 ]). :- use_module(library(lists)). /** <module> Weak arc consistent all_distinct/1 constraint @deprecated Superseded by library(clpfd)'s all_distinct/1. @author Markus Triska */ % For details, see Neng-Fa Zhou, 2005: % "Programming Finite-Domain Constraint Propagators in Action Rules" /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - This library uses the following arribute value: dom_neq(Domain, Left, Right) Domain is an unbounded (GMP) integer representing the domain as a bit-vector, meaning N is in the domain iff 0 =\= Domain /\ (1<<N). Left and Right are both lists of lists of variables. Each of those lists corresponds to one all_distinct constraint the variable is involved in, and "left" and "right" means literally which variables are to the left, and which to the right in the first, second etc. of those constraints. all_distinct([A,B,C,D]), all_distinct([X,Y,C,F,E]) causes the following attributes for "C": Left: [[A,B],[X,Y]] Right: [[D],[F,E]] - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */ vars_in(Xs, From, To) :- Bitvec is (1<<(To+1)) - (1<<From), vars_in_(Xs, Bitvec). vars_in(Xs, Dom) :- domain_bitvector(Dom, 0, Bitvec), vars_in_(Xs, Bitvec). vars_in_([], _). vars_in_([V|Vs], Bitvec) :- ( var(V) -> ( get_attr(V, clp_distinct, dom_neq(VBV,VLeft,VRight)) -> Bitvec1 is VBV /\ Bitvec, Bitvec1 =\= 0, ( popcount(Bitvec1) =:= 1 -> V is msb(Bitvec1) ; put_attr(V, clp_distinct, dom_neq(Bitvec1,VLeft,VRight)) ) ; ( popcount(Bitvec) =:= 1 -> V is msb(Bitvec) ; put_attr(V, clp_distinct, dom_neq(Bitvec, [], [])) ) ) ; 0 =\= Bitvec /\ (1<<V) ), vars_in_(Vs, Bitvec). domain_bitvector([], Bitvec, Bitvec). domain_bitvector([D|Ds], Bitvec0, Bitvec) :- Bitvec1 is Bitvec0 \/ (1 << D), domain_bitvector(Ds, Bitvec1, Bitvec). all_distinct(Ls) :- all_distinct(Ls, []), outof_reducer(Ls). outof_reducer([]). outof_reducer([X|Xs]) :- ( var(X) -> get_attr(X, clp_distinct, dom_neq(Dom,Lefts,Rights)), outof_reducer(Lefts, Rights, X, Dom) ; true ), outof_reducer(Xs). all_distinct([], _). all_distinct([X|Right], Left) :- \+ list_contains(Right, X), outof(X, Left, Right), all_distinct(Right, [X|Left]). outof(X, Left, Right) :- ( var(X) -> get_attr(X, clp_distinct, dom_neq(Dom, XLefts, XRights)), put_attr(X, clp_distinct, dom_neq(Dom, [Left|XLefts], [Right|XRights])) ; exclude_fire([Left], [Right], X) ). exclude_fire(Lefts, Rights, E) :- Mask is \ ( 1 << E), exclude_fire(Lefts, Rights, E, Mask). exclude_fire([], [], _, _). exclude_fire([Left|Ls], [Right|Rs], E, Mask) :- exclude_list(Left, E, Mask), exclude_list(Right, E, Mask), exclude_fire(Ls, Rs, E, Mask). exclude_list([], _, _). exclude_list([V|Vs], Val, Mask) :- ( var(V) -> get_attr(V, clp_distinct, dom_neq(VDom0,VLefts,VRights)), VDom1 is VDom0 /\ Mask, VDom1 =\= 0, ( popcount(VDom1) =:= 1 -> V is msb(VDom1) ; put_attr(V, clp_distinct, dom_neq(VDom1,VLefts,VRights)) ) ; V =\= Val ), exclude_list(Vs, Val, Mask). attr_unify_hook(dom_neq(Dom,Lefts,Rights), Y) :- ( ground(Y) -> Dom /\ (1 << Y) =\= 0, exclude_fire(Lefts, Rights, Y) ; \+ lists_contain(Lefts, Y), \+ lists_contain(Rights, Y), ( get_attr(Y, clp_distinct, dom_neq(YDom0,YLefts0,YRights0)) -> YDom1 is YDom0 /\ Dom, YDom1 =\= 0, ( popcount(YDom1) =:= 1 -> Y is msb(YDom1) ; append(YLefts0, Lefts, YLefts1), append(YRights0, Rights, YRights1), put_attr(Y, clp_distinct, dom_neq(YDom1,YLefts1,YRights1)) ) ; put_attr(Y, clp_distinct, dom_neq(Dom,Lefts,Rights)) ) ). lists_contain([X|Xs], Y) :- ( list_contains(X, Y) -> true ; lists_contain(Xs, Y) ). list_contains([X|Xs], Y) :- ( X == Y -> true ; list_contains(Xs, Y) ). outof_reducer([], [], _, _). outof_reducer([L|Ls], [R|Rs], Var, Dom) :- append(L, R, Others), N is popcount(Dom), num_subsets(Others, Dom, 0, Num), ( Num >= N -> fail ; Num =:= (N - 1) -> reduce_from_others(Others, Dom) ; true ), outof_reducer(Ls, Rs, Var, Dom). reduce_from_others([], _). reduce_from_others([X|Xs], Dom) :- ( var(X) -> get_attr(X, clp_distinct, dom_neq(XDom,XLeft,XRight)), ( is_subset(Dom, XDom) -> true ; NXDom is XDom /\ \Dom, NXDom =\= 0, ( popcount(NXDom) =:= 1 -> X is msb(NXDom) ; put_attr(X, clp_distinct, dom_neq(NXDom,XLeft,XRight)) ) ) ; true ), reduce_from_others(Xs, Dom). num_subsets([], _Dom, Num, Num). num_subsets([S|Ss], Dom, Num0, Num) :- ( var(S) -> get_attr(S, clp_distinct, dom_neq(SDom,_,_)), ( is_subset(Dom, SDom) -> Num1 is Num0 + 1 ; Num1 = Num0 ) ; Num1 = Num0 ), num_subsets(Ss, Dom, Num1, Num). % true iff S is a subset of Dom - should be a GMP binding (subsumption) is_subset(Dom, S) :- S \/ Dom =:= Dom. attr_portray_hook(dom_neq(Dom,_,_), _) :- Max is msb(Dom), Min is lsb(Dom), write(Min-Max).