org.chocosolver.solver.constraints.nary.sum.PropScalarWithLong Maven / Gradle / Ivy
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/*
* This file is part of choco-solver, http://choco-solver.org/
*
* Copyright (c) 2023, 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.sum;
import org.chocosolver.solver.constraints.Operator;
import org.chocosolver.solver.exception.ContradictionException;
import org.chocosolver.solver.variables.IntVar;
import org.chocosolver.util.ESat;
/**
* A propagator for SUM(x_i*c_i) = b
*
* Based on "Bounds Consistency Techniques for Long Linear Constraint"
* W. Harvey and J. Schimpf
*
*
* @author Charles Prud'homme
* @since 18/03/11
*/
public class PropScalarWithLong extends PropSumWithLong {
/**
* The coefficients
*/
private final long[] c;
/**
* Create a scalar product: SUM(x_i*c_i) o b
* Variables and coefficients are excepted to be ordered wrt to coefficients: first positive ones then negative ones.
* @param variables list of integer variables
* @param coeffs list of coefficients
* @param pos position of the last positive coefficient
* @param o operator
* @param b bound to respect.
*/
public PropScalarWithLong(IntVar[] variables, long[] coeffs, int pos, Operator o, long b) {
super(variables, pos, o, b);
this.c = coeffs;
}
@Override
protected void prepare() {
sumLB = sumUB = 0;
int i = 0;
long lb, ub;
maxI = 0;
for (; i < pos; i++) { // first the positive coefficients
lb = vars[i].getLB() * c[i];
ub = vars[i].getUB() * c[i];
sumLB += lb;
sumUB += ub;
I[i] = (ub - lb);
if(maxI < I[i])maxI = I[i];
}
for (; i < l; i++) { // then the negative ones
lb = vars[i].getUB() * c[i];
ub = vars[i].getLB() * c[i];
sumLB += lb;
sumUB += ub;
I[i] = (ub - lb);
if(maxI < I[i])maxI = I[i];
}
}
@Override
protected void filterOnEq() throws ContradictionException {
boolean anychange;
long F = b - sumLB;
long E = sumUB - b;
do {
anychange = false;
// When explanations are on, no global failure allowed
if (model.getSolver().isLearnOff() && F < 0 || E < 0) {
fails();
}
if (maxI > F || maxI > E) {
maxI = 0;
long lb, ub;
int i = 0;
// positive coefficients first
while (i < pos) {
if (I[i] - F > 0) {
lb = vars[i].getLB() * c[i];
ub = lb + I[i];
if (vars[i].updateUpperBound(divFloor(F + lb, c[i]), this)) {
long nub = vars[i].getUB() * c[i];
E += nub - ub;
I[i] = nub - lb;
anychange = true;
}
}
if (I[i] - E > 0) {
ub = vars[i].getUB() * c[i];
lb = ub - I[i];
if (vars[i].updateLowerBound(divCeil(ub - E, c[i]), this)) {
long nlb = vars[i].getLB() * c[i];
F -= nlb - lb;
I[i] = ub - nlb;
anychange = true;
}
}
if(maxI < I[i])maxI = I[i];
i++;
}
// then negative ones
while (i < l) {
if (I[i] - F > 0) {
lb = vars[i].getUB() * c[i];
ub = lb + I[i];
if (vars[i].updateLowerBound(divCeil(-F - lb, -c[i]), this)) {
long nub = vars[i].getLB() * c[i];
E += nub - ub;
I[i] = nub - lb;
anychange = true;
}
}
if (I[i] - E > 0) {
ub = vars[i].getLB() * c[i];
lb = ub - I[i];
if (vars[i].updateUpperBound(divFloor(-ub + E, -c[i]), this)) {
long nlb = vars[i].getUB() * c[i];
F -= nlb - lb;
I[i] = ub - nlb;
anychange = true;
}
}
if(maxI < I[i])maxI = I[i];
i++;
}
}
if (F <= 0 && E <= 0) {
this.setPassive();
return;
}
} while (anychange);
}
@Override
protected void filterOnLeq() throws ContradictionException {
long F = b - sumLB;
long E = sumUB - b;
// When explanations are on, no global failure allowed
if (model.getSolver().isLearnOff() &&F < 0) {
fails();
}
if (maxI > F) {
long lb, ub;
int i = 0;
maxI = 0;
// positive coefficients first
while (i < pos) {
maxI = 0;
if (I[i] - F > 0) {
lb = vars[i].getLB() * c[i];
ub = lb + I[i];
if (vars[i].updateUpperBound(divFloor(F + lb, c[i]), this)) {
long nub = vars[i].getUB() * c[i];
E += nub - ub;
I[i] = nub - lb;
}
}
if(maxI < I[i])maxI = I[i];
i++;
}
// then negative ones
while (i < l) {
if (I[i] - F > 0) {
lb = vars[i].getUB() * c[i];
ub = lb + I[i];
if (vars[i].updateLowerBound(divCeil(-F - lb, -c[i]), this)) {
long nub = vars[i].getLB() * c[i];
E += nub - ub;
I[i] = nub - lb;
}
}
if(maxI < I[i])maxI = I[i];
i++;
}
}
if (E <= 0) {
this.setPassive();
}
}
@Override
protected void filterOnGeq() throws ContradictionException {
long F = b - sumLB;
long E = sumUB - b;
// When explanations are on, no global failure allowed
if (model.getSolver().isLearnOff() && E < 0) {
fails();
}
if (maxI > E) {
maxI = 0;
long lb, ub;
int i = 0;
// positive coefficients first
while (i < pos) {
if (I[i] - E > 0) {
ub = vars[i].getUB() * c[i];
lb = ub - I[i];
if (vars[i].updateLowerBound(divCeil(ub - E, c[i]), this)) {
long nlb = vars[i].getLB() * c[i];
F -= nlb - lb;
I[i] = ub - nlb;
}
}
if(maxI < I[i])maxI = I[i];
i++;
}
// then negative ones
while (i < l) {
if (I[i] - E > 0) {
ub = vars[i].getLB() * c[i];
lb = ub - I[i];
if (vars[i].updateUpperBound(divFloor(-ub + E, -c[i]), this)) {
long nlb = vars[i].getUB() * c[i];
F -= nlb - lb;
I[i] = ub - nlb;
}
}
if(maxI < I[i])maxI = I[i];
i++;
}
}
if (F <= 0) {
this.setPassive();
}
}
@Override
protected void filterOnNeq() throws ContradictionException {
long F = b - sumLB;
long E = sumUB - b;
if (F < 0 || E < 0) {
setPassive();
return;
}
int w = -1;
long sum = 0;
for (int i = 0; i < l; i++) {
if (vars[i].isInstantiated()) {
sum += vars[i].getValue() * c[i];
} else if (w == -1) {
w = i;
} else return;
}
if (w == -1) {
if (sum == b) {
this.fails();
}
} else if(c[w]!=0 && (b - sum)%c[w]==0){
vars[w].removeValue((b - sum)/c[w], this);
}
}
@Override
public ESat isEntailed() {
long sumUB = 0, sumLB = 0;
int i = 0;
for (; i < pos; i++) { // first the positive coefficients
sumLB += vars[i].getLB() * c[i];
sumUB += vars[i].getUB() * c[i];
}
for (; i < l; i++) { // then the negative ones
sumLB += vars[i].getUB() * c[i];
sumUB += vars[i].getLB() * c[i];
}
return check(sumLB, sumUB);
}
@Override
public String toString() {
StringBuilder linComb = new StringBuilder(20);
linComb.append(c[0]).append('.').append(vars[0].getName());
int i = 1;
for (; i < pos; i++) {
linComb.append(" + ").append(c[i]).append('.').append(vars[i].getName());
}
for (; i < l; i++) {
linComb.append(" - ").append(-c[i]).append('.').append(vars[i].getName());
}
linComb.append(" ").append(o).append(" ");
linComb.append(b);
return linComb.toString();
}
private long divFloor(long a, long b) {
// we assume b > 0
if (a >= 0) {
return (a / b);
} else {
return (a - b + 1) / b;
}
}
private long divCeil(long a, long b) {
// we assume b > 0
if (a >= 0) {
return ((a + b - 1) / b);
} else {
return a / b;
}
}
@Override
protected PropScalarWithLong opposite(){
return new PropScalarWithLong(vars, c, pos, nop(o), b + nb(o));
}
}