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use square when possible and stronger filtering #1054

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use square when possible and stronger filtering #1054

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d11b7de
fix citation for AllDiffPrecMoreThanBc.java
ArthurGodet Aug 2, 2022
ffd68ce
Merge branch 'master' of https://github.com/chocoteam/choco-solver
ArthurGodet Oct 3, 2022
c0240fd
Merge branch 'master' of https://github.com/chocoteam/choco-solver
ArthurGodet Dec 18, 2022
94bd038
Merge branch 'master' of https://github.com/chocoteam/choco-solver
ArthurGodet Jun 25, 2023
5b7b50f
use square when possible and stronger filtering
jgFages Jul 21, 2023
7701fe8
propsquare filtering + test
jgFages Jul 24, 2023
96b8f5a
propsquare filter perfect squares at root node once and for all
jgFages Jul 24, 2023
42bfc35
squaretest independant of default search
jgFages Jul 25, 2023
59c4839
Merge branch 'master' of https://github.com/chocoteam/choco-solver
ArthurGodet Aug 1, 2023
67282af
Merge branch 'JG_square' of https://github.com/chocoteam/choco-solver…
ArthurGodet Aug 1, 2023
4e266e5
simplify code and add propagation tests
ArthurGodet Aug 1, 2023
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4 changes: 3 additions & 1 deletion solver/src/main/java/org/chocosolver/solver/constraints/IIntConstraintFactory.java
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Expand Up @@ -736,7 +736,9 @@ default Constraint mod(IntVar X, IntVar Y, IntVar Z) {
*/
@SuppressWarnings("SuspiciousNameCombination")
default Constraint times(IntVar X, IntVar Y, IntVar Z) {
if (Y.isInstantiated()) {
if (X == Y) {
return square(Z, X);
} else if (Y.isInstantiated()) {
return times(X, Y.getValue(), Z);
} else if (X.isInstantiated()) {
return times(Y, X.getValue(), Z);
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113 changes: 65 additions & 48 deletions solver/src/main/java/org/chocosolver/solver/constraints/binary/PropSquare.java
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Expand Up @@ -57,22 +57,11 @@ public void propagate(int evtmask) throws ContradictionException {
public ESat isEntailed() {
if (vars[0].getUB() < 0) {
return ESat.FALSE;
} else if (vars[0].isInstantiated()) {
if (vars[1].isInstantiated()) {
return ESat.eval(vars[0].getValue() == sqr(vars[1].getValue()));
} else if (vars[1].getDomainSize() == 2 &&
vars[1].contains(-floor_sqrt(vars[0].getValue())) &&
vars[1].contains(-floor_sqrt(vars[0].getValue()))) {
return ESat.TRUE;
} else if (!vars[1].contains(floor_sqrt(vars[0].getValue())) &&
!vars[1].contains(-floor_sqrt(vars[0].getValue()))) {
return ESat.FALSE;
} else {
return ESat.UNDEFINED;
}
} else {
return ESat.UNDEFINED;
}
if (isCompletelyInstantiated()) {
return ESat.eval(vars[0].getValue() == sqr(vars[1].getValue()));
}
return ESat.UNDEFINED;
}

@Override
Expand All @@ -89,14 +78,16 @@ private void setBounds() throws ContradictionException {
}

private static int floor_sqrt(int n) {
if (n < 0)
if (n < 0) {
return 0;
}
return (int) Math.floor(Math.sqrt(n));
}

private static int ceil_sqrt(int n) {
if (n < 0)
if (n < 0) {
return 0;
}
return (int) Math.ceil(Math.sqrt(n));
}

Expand All @@ -117,57 +108,95 @@ protected void updateLowerBoundofX() throws ContradictionException {

protected void updateUpperBoundofX() throws ContradictionException {
vars[0].updateUpperBound(Math.max(sqr(vars[1].getLB()), sqr(vars[1].getUB())), this);

}

protected boolean updateHolesinX() throws ContradictionException {
if (!vars[0].hasEnumeratedDomain()) {
return false;
}
boolean impact = false;
boolean isFirstPropagation = model.getSolver().getNodeCount() == 0;
if (isFirstPropagation) {
// check perfect squares once and for all
int ub = vars[0].getUB();
vrms.clear();
vrms.setOffset(vars[0].getLB());
for (int value = vars[0].getLB(); value <= ub; value = vars[0].nextValue(value)) {
if (!MathUtils.isPerfectSquare(value)) {
vrms.add(value);
}
}
impact = vars[0].removeValues(vrms, this);
}

// remove intervals to deal with consecutive value removal and upper bound modification
if (bothEnum) {
int ub = vars[0].getUB();
vrms.clear();
vrms.setOffset(vars[0].getLB());
for (int value = vars[0].getLB(); value <= ub; value = vars[0].nextValue(value)) {
if (!(MathUtils.isPerfectSquare(value) &&
(vars[1].contains(floor_sqrt(value)) || vars[1].contains(-floor_sqrt(value))))) {
int sqrt = floor_sqrt(value);
if (!vars[1].contains(sqrt) && !vars[1].contains(-sqrt)) {
vrms.add(value);
}
}
return vars[0].removeValues(vrms, this);
} else if (vars[0].hasEnumeratedDomain()) {
impact |= vars[0].removeValues(vrms, this);
} else {
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int value = vars[0].getLB();
int nlb = value - 1;
while (nlb == value - 1) {
if (!vars[1].contains(floor_sqrt(value)) && !vars[1].contains(-floor_sqrt(value))) {
int sqrt = floor_sqrt(value);
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if (!vars[1].contains(sqrt) && !vars[1].contains(-sqrt)) {
nlb = value;
}
value = vars[0].nextValue(value);
}
boolean filter = vars[0].updateLowerBound(nlb, this);
impact |= vars[0].updateLowerBound(nlb, this);

value = vars[0].getUB();
int nub = value + 1;
while (nub == value + 1) {
if (!vars[1].contains(floor_sqrt(value)) && !vars[1].contains(-floor_sqrt(value))) {
int sqrt = floor_sqrt(value);
if (!vars[1].contains(sqrt) && !vars[1].contains(-sqrt)) {
nub = value;
}
value = vars[0].previousValue(value);
}
return filter | vars[0].updateUpperBound(nub, this);
impact |= vars[0].updateUpperBound(nub, this);
}
return false;
return impact;
}

protected boolean updateLowerBoundofY() throws ContradictionException {
return vars[1].updateLowerBound(-ceil_sqrt(vars[0].getUB()), this);
if (vars[1].getLB() >= 0) {
return vars[1].updateLowerBound(ceil_sqrt(vars[0].getLB()), this);
} else {
return vars[1].updateLowerBound(-floor_sqrt(vars[0].getUB()), this);
}
}

protected boolean updateUpperBoundofY() throws ContradictionException {
return vars[1].updateUpperBound(floor_sqrt(vars[0].getUB()), this);
if (vars[1].getUB() < 0) {
return vars[1].updateUpperBound(-ceil_sqrt(vars[0].getLB()), this);
} else {
return vars[1].updateUpperBound(floor_sqrt(vars[0].getUB()), this);
}
}

protected boolean updateHolesinY() throws ContradictionException {
// remove intervals to deal with consecutive value removal and upper bound modification
if (bothEnum) {
if (vars[0].isInstantiatedTo(0)) {
return vars[1].instantiateTo(0, this);
}
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boolean impact = false;
// remove interval around 0 based on X LB
if (vars[1].hasEnumeratedDomain()) {
int val = ceil_sqrt(vars[0].getLB()) - 1;
if (val >= 0) {
impact = vars[1].removeInterval(-val, val, this);
}
}
// remove values based on X holes
if (bothEnum && hasHoles(vars[0])) {
int ub = vars[1].getUB();
vrms.clear();
vrms.setOffset(vars[1].getLB());
Expand All @@ -176,24 +205,12 @@ protected boolean updateHolesinY() throws ContradictionException {
vrms.add(value);
}
}
return vars[1].removeValues(vrms, this);
} else if (vars[1].hasEnumeratedDomain()) {
int lb = vars[1].getLB();
int ub = vars[1].getUB();
while (!vars[0].contains(sqr(lb))) {
lb = vars[1].nextValue(lb);
if (lb > ub) break;
}
boolean filter = vars[1].updateLowerBound(lb, this);

while (!vars[0].contains(sqr(ub))) {
ub = vars[1].nextValue(ub);
if (ub < lb) break;
}
return filter | vars[1].updateUpperBound(ub, this);
impact |= vars[1].removeValues(vrms, this);
}
return false;
return impact;
}


private boolean hasHoles(IntVar var) {
return (var.getUB() - var.getLB() + 1) > var.getDomainSize();
}
}
51 changes: 51 additions & 0 deletions solver/src/test/java/org/chocosolver/solver/constraints/binary/SquareTest.java
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Expand Up @@ -23,6 +23,57 @@
*/
public class SquareTest {

@Test(groups = "10s", timeOut = 60000)
public void testBigBoundBound() {
Model m = new Model();
int n = 6;
IntVar[] x = m.intVarArray(n, -n, n, true);
IntVar[] x2 = m.intVarArray(n, -n*n,n*n, true);
for (int i=0;i<x.length;i++) {
m.square(x2[i], x[i]).post();
}
m.allDifferent(x).post();
m.allDifferent(x2).post();
while (m.getSolver().solve()) ;
assertEquals(m.getSolver().getSolutionCount(), 184320);
assertEquals(m.getSolver().getFailCount(), 209153);
assertEquals(m.getSolver().getNodeCount(), 577792);
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}

@Test(groups = "10s", timeOut = 60000)
public void testBigEnumBound() {
Model m = new Model();
int n = 6;
IntVar[] x = m.intVarArray(n, -n, n, false);
IntVar[] x2 = m.intVarArray(n, -n*n,n*n, true);
for (int i=0;i<x.length;i++) {
m.square(x2[i], x[i]).post();
}
m.allDifferent(x).post();
m.allDifferent(x2).post();
while (m.getSolver().solve()) ;
assertEquals(m.getSolver().getSolutionCount(), 184320);
assertEquals(m.getSolver().getFailCount(), 28397);
assertEquals(m.getSolver().getNodeCount(), 397036);
}

@Test(groups = "10s", timeOut = 60000)
public void testBigEnumEnum() {
Model m = new Model();
int n = 6;
IntVar[] x = m.intVarArray(n, -n, n, false);
IntVar[] x2 = m.intVarArray(n, -n*n,n*n, false);
for (int i=0;i<x.length;i++) {
m.square(x2[i], x[i]).post();
}
m.allDifferent(x).post();
m.allDifferent(x2).post();
while (m.getSolver().solve()) ;
assertEquals(m.getSolver().getSolutionCount(), 184320);
assertEquals(m.getSolver().getFailCount(), 0);
assertEquals(m.getSolver().getNodeCount(), 368639);
}

@Test(groups = "1s", timeOut = 60000)
public void testCst() {
Model m = new Model();
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