1/* 2 3 Part of CLP(Q,R) (Constraint Logic Programming over Rationals and Reals) 4 5 Author: Leslie De Koninck 6 E-mail: Leslie.DeKoninck@cs.kuleuven.be 7 WWW: http://www.swi-prolog.org 8 http://www.ai.univie.ac.at/cgi-bin/tr-online?number+95-09 9 Copyright (C): 2006, K.U. Leuven and 10 1992-1995, Austrian Research Institute for 11 Artificial Intelligence (OFAI), 12 Vienna, Austria 13 14 This software is based on CLP(Q,R) by Christian Holzbaur for SICStus 15 Prolog and distributed under the license details below with permission from 16 all mentioned authors. 17 18 This program is free software; you can redistribute it and/or 19 modify it under the terms of the GNU General Public License 20 as published by the Free Software Foundation; either version 2 21 of the License, or (at your option) any later version. 22 23 This program is distributed in the hope that it will be useful, 24 but WITHOUT ANY WARRANTY; without even the implied warranty of 25 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 26 GNU General Public License for more details. 27 28 You should have received a copy of the GNU Lesser General Public 29 License along with this library; if not, write to the Free Software 30 Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA 31 32 As a special exception, if you link this library with other files, 33 compiled with a Free Software compiler, to produce an executable, this 34 library does not by itself cause the resulting executable to be covered 35 by the GNU General Public License. This exception does not however 36 invalidate any other reasons why the executable file might be covered by 37 the GNU General Public License. 38*/ 39 40% 41% Answer constraint projection 42% 43 44:- module(clpcd_project, 45 [ 46 drop_dep/1, 47 drop_dep_one/1, 48 make_target_indep/2 49 ]). 50 51:- use_module(library(clpcd/indep)). 52:- use_module(library(clpcd/solve)). 53 54% 55% Collect the pivots in reverse order 56% We have to protect the target variables pivot partners 57% from redundancy eliminations triggered by fm_elim, 58% in order to allow for reverse pivoting. 59% 60make_target_indep(Ts,Ps) :- make_target_indep(Ts,[],Ps). 61 62% make_target_indep(Targets,Pivots,PivotsTail) 63% 64% Tries to make as many targetvariables independent by pivoting them with a non-target 65% variable. The pivots are stored as T:NT where T is a target variable and NT a non-target 66% variable. The non-target variables are marked to be kept during redundancy eliminations. 67 68make_target_indep([],Ps,Ps). 69make_target_indep([T|Ts],Ps0,Pst) :- 70 ( get_attr(T,clpcd_itf,AttT), 71 arg(1,AttT,CLP), 72 arg(2,AttT,type(Type)), 73 arg(4,AttT,lin([_,_|H])), 74 nontarget(H,Nt) 75 -> Ps1 = [T:Nt|Ps0], 76 get_attr(Nt,clpcd_itf,AttN), 77 arg(2,AttN,type(IndAct)), 78 arg(5,AttN,order(Ord)), 79 arg(6,AttN,class(Class)), 80 setarg(11,AttN,keep), 81 pivot(CLP,T,Class,Ord,Type,IndAct) 82 ; Ps1 = Ps0 83 ), 84 make_target_indep(Ts,Ps1,Pst). 85 86% nontarget(Hom,Nt) 87% 88% Finds a nontarget variable in homogene part Hom. 89% Hom contains elements of the form l(V*K,OrdV). 90% A nontarget variable has no target attribute and no keep_indep attribute. 91 92nontarget([l(V*_,_)|Vs],Nt) :- 93 ( get_attr(V,clpcd_itf,Att), 94 arg(9,Att,n), 95 arg(10,Att,n) 96 -> Nt = V 97 ; nontarget(Vs,Nt) 98 ). 99 100% drop_dep(Vars) 101% 102% Does drop_dep_one/1 on each variable in Vars. 103 104drop_dep(Vs) :- 105 var(Vs), 106 !. 107drop_dep([]). 108drop_dep([V|Vs]) :- 109 drop_dep_one(V), 110 drop_dep(Vs). 111 112% drop_dep_one(V) 113% 114% If V is an unbounded dependent variable that isn't a target variable, shouldn't be kept 115% and is not nonzero, drops all linear attributes of V. 116% The linear attributes are: type, strictness, linear equation (lin), class and order. 117 118drop_dep_one(V) :- 119 get_attr(V,clpcd_itf,Att), 120 Att = t(CLP,type(t_none),_,lin(Lin),order(OrdV),_,_,n,n,_,n), 121 \+ indep(CLP,Lin,OrdV), 122 !, 123 setarg(2,Att,n), 124 setarg(3,Att,n), 125 setarg(4,Att,n), 126 setarg(5,Att,n), 127 setarg(6,Att,n). 128drop_dep_one(_)