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Make propagation stops sooner if time limit is met (fix issue #1062) #1064

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Make propagation stops sooner if time limit is met (fix issue #1062) #1064

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4c136b1
make propagation stops sooner if time limit is met (fix issue #1062)
ArthurGodet Oct 9, 2023
b512e4d
fix NullPointerException wrt TimeCounter in Solver
ArthurGodet Oct 9, 2023
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26 changes: 24 additions & 2 deletions solver/src/main/java/org/chocosolver/solver/Solver.java
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Original file line number Diff line number Diff line change
Expand Up @@ -21,6 +21,7 @@
import org.chocosolver.solver.propagation.PropagationEngine;
import org.chocosolver.solver.search.SearchState;
import org.chocosolver.solver.search.limits.ICounter;
import org.chocosolver.solver.search.limits.TimeCounter;
import org.chocosolver.solver.search.loop.Reporting;
import org.chocosolver.solver.search.loop.learn.Learn;
import org.chocosolver.solver.search.loop.learn.LearnNothing;
Expand Down Expand Up @@ -169,6 +170,8 @@ public enum Action {
*/
protected List<Criterion> criteria;

protected TimeCounter timeCounter;

/**
* Indicates if the default search loop is in use (set to <tt>true</tt> in that case).
*/
Expand Down Expand Up @@ -1007,11 +1010,21 @@ public boolean hasEndedUnexpectedly() {
return mMeasures.getSearchState() == SearchState.KILLED;
}

/**
* @return <tt>true</tt> if the time limit is met.
*/
public boolean isTimeLimitMet() {
if (timeCounter != null) {
return timeCounter.isMet();
}
return false;
}

/**
* @return <tt>true</tt> if the search loops encountered at least one of the stop criteria declared.
*/
public boolean isStopCriterionMet() {
boolean ismet = false;
boolean ismet = isTimeLimitMet();
for (int i = 0; i < criteria.size() && !ismet; i++) {
ismet = criteria.get(i).isMet();
}
Expand Down Expand Up @@ -1311,7 +1324,16 @@ public void removeHints() {
*/
public void addStopCriterion(Criterion... criterion) {
if (criterion != null) {
Collections.addAll(criteria, criterion);
for (int i = 0; i < criterion.length; i++) {
if (criterion[i] instanceof TimeCounter) {
TimeCounter tc = (TimeCounter) criterion[i];
if (timeCounter == null || timeCounter.getLimitValue() > tc.getLimitValue()) {
timeCounter = tc;
}
} else {
criteria.add(criterion[i]);
}
}
}
}

Expand Down
3 changes: 3 additions & 0 deletions solver/src/main/java/org/chocosolver/solver/propagation/PropagationEngine.java
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Expand Up @@ -189,6 +189,9 @@ public void propagate() throws ContradictionException {
manageModifications();
for (int i = nextNotEmpty(); i > -1; i = nextNotEmpty()) {
assert !pro_queue[i].isEmpty() : "try to pop a propagator from an empty queue";
if (model.getSolver().isTimeLimitMet()) {
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why not calling model.getSolver().isStopCriterionMet() ?
This would avoid modifying the Solver class.

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The idea was to have a simple check on the time limit, and not check all the stopping criterion before the propagation of each propagator.
Indeed, all stopping criterion but the time limit do not depend on the problem's state outside of fixpoint. Unless you can think of one that would.

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Personnaly, I would have move the code to the end of the while-loop just to keep the main purpose (ie, propagating) clear

return;
}
lastProp = pro_queue[i].pollFirst();
if (pro_queue[i].isEmpty()) {
notEmpty &= ~(1 << i);
Expand Down
32 changes: 32 additions & 0 deletions solver/src/test/java/org/chocosolver/solver/LimitsTest.java
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Expand Up @@ -9,12 +9,15 @@
*/
package org.chocosolver.solver;

import org.chocosolver.solver.exception.SolverException;
import org.chocosolver.solver.variables.IntVar;
import org.chocosolver.util.tools.TimeUtils;
import org.testng.Assert;
import org.testng.annotations.Test;

import static org.chocosolver.util.ProblemMaker.makeNQueenWithBinaryConstraints;
import static org.testng.Assert.assertEquals;
import static org.testng.Assert.assertFalse;
import static org.testng.Assert.assertTrue;

/**
Expand All @@ -35,6 +38,35 @@ public void testTime() {
assertTrue(tl - (tl * 5 / 100) <= tc && tc <= tl + (tl * 5 / 100), tl + " vs. " + tc);
}

@Test(groups="1s", timeOut=60000)
public void testTime2() throws SolverException {
Model model = new Model();

IntVar v7 = model.intVar("@v7", IntVar.MIN_INT_BOUND, IntVar.MAX_INT_BOUND, true);

model.post(
model.arithm(v7, ">", v7),
model.arithm(v7, "<", v7)
);
// TODO : such a simple case should be detected within the constraint declaration
// TODO : this test might need to be changed if better model analysis is done during model declaration

Solver solver = model.getSolver();
solver.limitTime(250);

long start = System.currentTimeMillis();
boolean solved = solver.solve();
long took = System.currentTimeMillis() - start;

assertFalse(solved);
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Good to check that solve() returns false;

assertEquals(solver.getNodeCount(), 1);
assertEquals(solver.getBackTrackCount(), 0);
assertEquals(solver.getFailCount(), 0);
assertEquals(solver.getSolutionCount(), 0);
assertTrue(solver.isStopCriterionMet());
assertTrue(took <= 1000); // less than 1 second
}

@Test(groups="1s", timeOut=60000)
public void testNode() {
Model s = makeNQueenWithBinaryConstraints(12);
Expand Down