Jip J. Dekker
1d9faf38de
git-subtree-dir: software/gecode git-subtree-split: 313e87646da4fc2752a70e83df16d993121a8e40
247 lines
8.0 KiB
C++
247 lines
8.0 KiB
C++
/* -*- mode: C++; c-basic-offset: 2; indent-tabs-mode: nil -*- */
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/*
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* Main authors:
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* Patrick Pekczynski <pekczynski@ps.uni-sb.de>
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*
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* Copyright:
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* Patrick Pekczynski, 2004
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*
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* This file is part of Gecode, the generic constraint
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* development environment:
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* http://www.gecode.org
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*
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* Permission is hereby granted, free of charge, to any person obtaining
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* a copy of this software and associated documentation files (the
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* "Software"), to deal in the Software without restriction, including
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* without limitation the rights to use, copy, modify, merge, publish,
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* distribute, sublicense, and/or sell copies of the Software, and to
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* permit persons to whom the Software is furnished to do so, subject to
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* the following conditions:
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*
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* The above copyright notice and this permission notice shall be
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* included in all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
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* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
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* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
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* NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
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* LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
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* OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
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* WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
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*
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*/
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namespace Gecode { namespace Int { namespace Sorted {
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/**
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* \brief Compute the sccs of the oriented intersection-graph
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*
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* An y-node \f$y_j\f$ and its corresponding matching mate
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* \f$x_{\phi(j)}\f$ form the smallest possible scc, since both
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* edges \f$e_1(y_j, x_{\phi(j)})\f$ and \f$e_2(x_{\phi(j)},y_j)\f$
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* are both contained in the oriented intersection graph.
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*
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* Hence a scc containg more than two nodes is represented as an
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* array of SccComponent entries,
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* \f$[ y_{j_0},x_{\phi(j_0)},\dots,y_{j_k},x_{\phi(j_k)}]\f$.
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*
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* Parameters
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* scclist ~ resulting sccs
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*/
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template<class View>
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inline void
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computesccs(ViewArray<View>& x, ViewArray<View>& y,
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int phi[], SccComponent sinfo[], int scclist[]) {
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// number of sccs is bounded by xs (number of x-nodes)
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int xs = x.size();
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Region r;
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Support::StaticStack<int,Region> cs(r,xs);
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//select an y node from the graph
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for (int j = 0; j < xs; j++) {
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int yjmin = y[j].min(); // the processed min
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while (!cs.empty() && x[phi[sinfo[cs.top()].rightmost]].max() < yjmin) {
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// the topmost scc cannot "reach" y_j or a node to the right of it
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cs.pop();
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}
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// a component has the form C(y-Node, matching x-Node)
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// C is a minimal scc in the oriented intersection graph
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// we only store y_j-Node, since \phi(j) gives the matching X-node
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int i = phi[j];
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int ximin = x[i].min();
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while (!cs.empty() && ximin <= y[sinfo[cs.top()].rightmost].max()) {
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// y_j can "reach" cs.top() ,
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// i.e. component c can reach component cs.top()
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// merge c and cs.top() into new component
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int top = cs.top();
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// connecting
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sinfo[sinfo[j].leftmost].left = top;
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sinfo[top].right = sinfo[j].leftmost;
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// moving leftmost
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sinfo[j].leftmost = sinfo[top].leftmost;
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// moving rightmost
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sinfo[sinfo[top].leftmost].rightmost = j;
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cs.pop();
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}
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cs.push(j);
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}
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cs.reset();
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// now we mark all components with the respective scc-number
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// labeling is bound by O(k) which is bound by O(n)
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for (int i = 0; i < xs; i++) {
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if (sinfo[i].left == i) { // only label variables in sccs
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int scc = sinfo[i].rightmost;
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int z = i;
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//bound by the size of the largest scc = k
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while (sinfo[z].right != z) {
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sinfo[z].rightmost = scc;
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scclist[phi[z]] = scc;
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z = sinfo[z].right;
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}
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sinfo[z].rightmost = scc;
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scclist[phi[z]] = scc;
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}
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}
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}
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/**
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* \brief Narrowing the domains of the x variables
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*
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* Due to the correspondance between perfect matchings in the "reduced"
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* intersection graph of \a x and \a y views and feasible
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* assignments for the sorted constraint the new domain bounds for
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* views in \a x are computed as
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* - lower bounds:
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* \f$ S_i \geq E_l \f$
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* where \f$y_l\f$ is the leftmost neighbour of \f$x_i\f$
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* - upper bounds:
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* \f$ S_i \leq E_h \f$
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* where \f$y_h\f$ is the rightmost neighbour of \f$x_i\f$
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*/
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template<class View, bool Perm>
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inline bool
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narrow_domx(Space& home,
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ViewArray<View>& x,
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ViewArray<View>& y,
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ViewArray<View>& z,
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int tau[],
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int[],
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int scclist[],
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SccComponent sinfo[],
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bool& nofix) {
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int xs = x.size();
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// For every x node
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for (int i = 0; i < xs; i++) {
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int xmin = x[i].min();
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/*
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* take the scc-list for the current x node
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* start from the leftmost reachable y node of the scc
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* and check which Y node in the scc is
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* really the rightmost node intersecting x, i.e.
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* search for the greatest lower bound of x
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*/
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int start = sinfo[scclist[i]].leftmost;
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while (y[start].max() < xmin) {
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start = sinfo[start].right;
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}
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if (Perm) {
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// start is the leftmost-position for x_i
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// that denotes the lower bound on p_i
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ModEvent me_plb = z[i].gq(home, start);
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if (me_failed(me_plb)) {
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return false;
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}
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nofix |= (me_modified(me_plb) && start != z[i].min());
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}
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ModEvent me_lb = x[i].gq(home, y[start].min());
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if (me_failed(me_lb)) {
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return false;
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}
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nofix |= (me_modified(me_lb) &&
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y[start].min() != x[i].min());
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int ptau = tau[xs - 1 - i];
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int xmax = x[ptau].max();
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/*
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* take the scc-list for the current x node
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* start from the rightmost reachable node and check which
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* y node in the scc is
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* really the rightmost node intersecting x, i.e.
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* search for the smallest upper bound of x
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*/
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start = sinfo[scclist[ptau]].rightmost;
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while (y[start].min() > xmax) {
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start = sinfo[start].left;
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}
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if (Perm) {
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//start is the rightmost-position for x_i
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//that denotes the upper bound on p_i
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ModEvent me_pub = z[ptau].lq(home, start);
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if (me_failed(me_pub)) {
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return false;
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}
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nofix |= (me_modified(me_pub) && start != z[ptau].max());
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}
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ModEvent me_ub = x[ptau].lq(home, y[start].max());
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if (me_failed(me_ub)) {
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return false;
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}
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nofix |= (me_modified(me_ub) &&
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y[start].max() != x[ptau].max());
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}
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return true;
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}
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/**
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* \brief Narrowing the domains of the y views
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*
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* analogously to the x views we take
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* - for the upper bounds the matching \f$\phi\f$ computed in glover
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* and compute the new upper bound by \f$T_j=min(E_j, D_{\phi(j)})\f$
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* - for the lower bounds the matching \f$\phi'\f$ computed in revglover
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* and update the new lower bound by \f$T_j=max(E_j, D_{\phi'(j)})\f$
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*/
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template<class View>
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inline bool
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narrow_domy(Space& home,
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ViewArray<View>& x, ViewArray<View>& y,
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int phi[], int phiprime[], bool& nofix) {
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for (int i=x.size(); i--; ) {
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ModEvent me_lb = y[i].gq(home, x[phiprime[i]].min());
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if (me_failed(me_lb)) {
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return false;
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}
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nofix |= (me_modified(me_lb) &&
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x[phiprime[i]].min() != y[i].min());
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ModEvent me_ub = y[i].lq(home, x[phi[i]].max());
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if (me_failed(me_ub)) {
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return false;
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}
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nofix |= (me_modified(me_ub) &&
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x[phi[i]].max() != y[i].max());
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}
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return true;
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}
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}}}
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// STATISTICS: int-prop
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