org.chocosolver.solver.constraints.nary.clauses.PropSignedClause Maven / Gradle / Ivy
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/*
* This file is part of choco-solver, http://choco-solver.org/
*
* Copyright (c) 2020, IMT Atlantique. All rights reserved.
*
* Licensed under the BSD 4-clause license.
*
* See LICENSE file in the project root for full license information.
*/
package org.chocosolver.solver.constraints.nary.clauses;
import org.chocosolver.solver.Solver;
import org.chocosolver.solver.constraints.Propagator;
import org.chocosolver.solver.constraints.PropagatorPriority;
import org.chocosolver.solver.exception.ContradictionException;
import org.chocosolver.solver.learn.ExplanationForSignedClause;
import org.chocosolver.solver.learn.Implications;
import org.chocosolver.solver.variables.IntVar;
import org.chocosolver.solver.variables.events.IntEventType;
import org.chocosolver.util.ESat;
import org.chocosolver.util.objects.ValueSortedMap;
import org.chocosolver.util.objects.setDataStructures.iterable.IntIterableRangeSet;
import org.chocosolver.util.tools.ArrayUtils;
import static org.chocosolver.util.ESat.FALSE;
import static org.chocosolver.util.ESat.TRUE;
import static org.chocosolver.util.ESat.UNDEFINED;
/**
* This propagator manages a signed clause: a disjunction of unary membership constraints.
*
* Project: choco-solver.
*
* @author Charles Prud'homme
* @since 11/05/2018.
*/
@SuppressWarnings("Duplicates")
public class PropSignedClause extends Propagator {
/**
* Free mask
*/
private static final byte F0 = 0b00;
/**
* Mask that indicates pos[0] as false
*/
private static final byte F1 = 0b01;
/**
* Mask that indicates pos[1] as false
*/
protected static final byte F2 = 0b10;
/**
* Store which pos, among 0 and 1, are false
*/
private byte FL;
/**
* List of variables this propagators deal with.
*/
private final IntVar[] mvars;
private final int[] bounds;
/**
* Literals of the clauses. Use to always get at position 0 a free literal.
*/
private final int[] pos;
private final Solver mSolver;
/**
* Store label of last activity
*/
public long label;
private static PropagatorPriority computePriority(int nbvars) {
if (nbvars == 2) {
return PropagatorPriority.BINARY;
} else if (nbvars == 3) {
return PropagatorPriority.TERNARY;
} else {
return PropagatorPriority.LINEAR;
}
}
/**
* Create a {@link PropSignedClause} instance considering that 'ranges' are allowed:
*
* ( ... ∨ vars[i] ∈ ranges[i] ∨ ... )
*
* @param vars set of variables
* @param ranges set of allowed ranges
* @return a instance of {@link PropSignedClause}
*/
public static PropSignedClause makeFromIn(IntVar[] vars, IntIterableRangeSet[] ranges){
return new PropSignedClause(vars, ranges, true);
}
/**
* Create a {@link PropSignedClause} instance considering that 'ranges' are forbidden:
*
* ( ... ∨ vars[i] ∉ ranges[i] ∨ ... )
* @param vars set of variables
* @param ranges set of allowed ranges
* @return a instance of {@link PropSignedClause}
*/
public static PropSignedClause makeFromOut(IntVar[] vars, IntIterableRangeSet[] ranges){
return new PropSignedClause(vars, ranges, false);
}
private PropSignedClause(IntVar[] vars, IntIterableRangeSet[] ranges, boolean in) {
super(new IntVar[]{vars[0], vars[1]}, computePriority(vars.length), false, true);
assert in;
// TODO: accurately select literals
this.mSolver = vars[0].getModel().getSolver();
int size = 0;
for (int i = 0; i < ranges.length; i++) {
size += ranges[i].getNbRanges();
}
this.pos = ArrayUtils.array(0, size - 1);
this.mvars = new IntVar[size];
this.bounds = new int[size << 1];
for (int i = 0, k = -1; i < ranges.length; i++) {
for (int r = 0; r < ranges[i].getNbRanges(); r++) {
this.mvars[++k] = vars[i];
this.bounds[k << 1] = ranges[i].minOfRange(r);
this.bounds[(k << 1) + 1] = ranges[i].maxOfRange(r);
}
}
if (ranges[0].getNbRanges() > 1) {
// synchronize positions of var[0] and var[1]
int nbr = ranges[0].getNbRanges();
int p = this.pos[1];
this.pos[1] = this.pos[nbr];
this.pos[nbr] = p;
}
// System.out.println(this);
}
@Override
public final int getPropagationConditions(int vIdx) {
assert vIdx <= 1;
assert vars[vIdx] == mvars[pos[vIdx]];
return IntEventType.boundAndInst();//all();
}
public void forceActivation(){
setActive0();
}
/**
* @return the number of literals in this
*/
public final int cardinality() {
return mvars.length;
}
private ESat check(int p) {
IntVar v = mvars[p];
int lv = v.getLB();
int uv = v.getUB();
int l = bounds[p << 1];
int u = bounds[(p << 1) + 1];
if (l <= lv && uv <= u) { // v in [l,u]
return ESat.TRUE;
} else if (l > uv || lv > u || (v.hasEnumeratedDomain() && v.nextValue(l - 1) > u)) { // v does not intersect [l,u]
return ESat.FALSE;
}
return ESat.UNDEFINED;
}
private boolean restrict(int p) throws ContradictionException {
return mvars[p].updateBounds(bounds[p << 1], bounds[(p << 1) + 1], this);
}
@SuppressWarnings("Duplicates")
public final void propagate(int evtmask) throws ContradictionException {
switch (check(pos[0])) {
case TRUE:
FL = F0;
label = -this.mSolver.getDecisionPath().size();
setPassive();
return;
case FALSE:
FL |= F1;
break;
case UNDEFINED:
break;
}
switch (check(pos[1])) {
case TRUE:
FL = F0;
label = -this.mSolver.getDecisionPath().size();
setPassive();
return;
case FALSE:
FL |= F2;
break;
case UNDEFINED:
break;
}
if (FL != F0) {
propagateClause();
}
}
/**
* Condition: at least one lit is false and none is true among l0 and l1.
*/
private void propagateClause() throws ContradictionException {
int k = 2;
int to = pos.length;
do {
int p;
if ((FL & F2) != 0) {
p = 1;
FL ^= F2;
} else {
p = 0;
FL ^= F1;
}
// assertion: p is false
int l0 = pos[0];
int l1 = pos[1];
if (p == 0) {
// Make sure the false literal is pos[1]:
int t = l0;
pos[0] = l0 = l1;
pos[1] = l1 = t;
swap();
}
// Look for new watch:
boolean cont = false;
for (; k < to; k++) {
int l = pos[k];
ESat b = check(l);
if (b != FALSE) {
// update watcher -- preserve the operations order
if (vars[1] != mvars[l]) {
vars[1].unlink(this, 1);
setVIndices(1, mvars[l].link(this, 1));
vars[1] = mvars[l];
}
pos[1] = l;
pos[k] = pos[--to];
pos[to] = l1;
if (b == TRUE) {
label = -this.mSolver.getDecisionPath().size();
setPassive();
FL = F0;
assert this.isEntailed() == TRUE;
return;
}
cont = true;
break;
}
}
// Did not find watch -- clause is unit under assignment:
if (!cont) {
FL = F0;
if (restrict(l0)) {
assert this.isEntailed() == TRUE;
label = this.mSolver.getDecisionPath().size();
setPassive();
return;
} else {
assert this.isEntailed() != FALSE;
}
}
} while (FL != F0);
}
private void swap() {
// update propagator internal structure
// 0. get temp var
IntVar v = this.vars[1];
// 1. swap variables
vars[1] = vars[0];
vars[0] = v;
int vi0 = getVIndice(0);
assert vars[1].getIndexInPropagator(vi0) == 0;
int vi1 = getVIndice(1);
assert vars[0].getIndexInPropagator(vi1) == 1;
// 2. swap pindices
this.vars[0].setPIndice(vi1, 0);
this.vars[1].setPIndice(vi0, 1);
// 3. swap vindices
setVIndices(0, vi1);
setVIndices(1, vi0);
}
int getNbFalsified() {
int count = 0;
for (int i = 0; i < pos.length; i++) {
ESat b = check(i);
if (b == FALSE) {
count++;
}
}
return count;
}
int getNbSatisfied() {
int count = 0;
for (int i = 0; i < pos.length; i++) {
ESat b = check(i);
if (b == TRUE) {
count++;
}
}
return count;
}
/**
* Test if one clause outshines another one or is incomparable with it.
* A clause ci outshines a clause cj iff:
*
* - var(ci) ⊆ var(cj) and
* - for each v in var(ci), rang(v, ci) ⊆ rang(v, cj)
*
* @implSpec vars in each clause is supposed to be sorted wrt the var ID.
* Otherwise, this method can return incorrect results.
* @param cj another clause
* @return negative integer, zero, or a positive integer as ci outshines,
* is not comparable with or is outshone by cj.
*/
final int dominate(PropSignedClause cj) {
if (this.mvars.length < cj.mvars.length) {
return outhsine0(this, cj);
} else if (this.mvars.length > cj.mvars.length) {
return -outhsine0(cj, this);
} else {
return outhsine1(this, cj);
}
}
/**
* Considering |ci| < |cj|, test if ci outshines cj.
* @implSpec variables, in each clause, are supposed to be sorted wrt to increasing ID.
* @param ci a clause
* @param cj another clause
* @return 1 if ci outshines cj, 0 otherwise
*/
private int outhsine0(PropSignedClause ci, PropSignedClause cj){
return 0;
}
/**
* Considering two clauses with same cardinality, check which one outshines the other, if any.
* @implSpec variables, in each clause, are supposed to be sorted wrt to increasing ID.
* @param ci a clause
* @param cj another clause
* @return 1, 0 or -1 as ci outshines cj, ci and cj are incomparable or cj oushines ci.
*/
private int outhsine1(PropSignedClause ci, PropSignedClause cj){
return 0;
}
public final ESat isEntailed() {
int i = 0;
boolean u = false;
while (i < pos.length) {
ESat b = check(i);
if (b == TRUE) {
return TRUE;
} else if (b == UNDEFINED) {
u = true;
}
i++;
}
return u ? UNDEFINED : FALSE;
}
public void explain(ExplanationForSignedClause explanation, ValueSortedMap front, Implications ig, int p) {
IntVar pivot = ig.getIntVarAt(p);
IntIterableRangeSet set;
int i = 0;
while (i < mvars.length) {
IntVar v = mvars[i];
if (front.getValueOrDefault(v, -1) == -1) { // see javadoc for motivation of these two lines
ig.findPredecessor(front, v, p);
}
set = explanation.getFreeSet();
do {
set.addBetween(bounds[i << 1], bounds[(i << 1) + 1]);
i++;
} while (i < mvars.length && mvars[i - 1] == mvars[i]);
explanation.addLiteral(v, set, (v == pivot));
}
}
@Override
public String toString() {
StringBuilder st = new StringBuilder();
st.append('(').append(mvars[pos[0]]).append(" \u2208 [")
.append(bounds[pos[0] << 1]).append(',').append(bounds[(pos[0] << 1) + 1]).append(']');
st.append(':').append(check(pos[0]));
for (int i = 1; i < pos.length; i++) {
st.append(") \u2228 (");
st.append(mvars[pos[i]]).append(" \u2208 [").append(bounds[pos[i] << 1])
.append(',').append(bounds[(pos[i] << 1) + 1]).append(']');
st.append(':').append(check(pos[i]));
}
st.append(')');
return st.toString();
}
}