PLANNER-1064 Solver.getTimeMillisSpent() and Solver.getBestScore() ne…

…ed to be thread safe

optaplanner-core/src/main/java/org/optaplanner/core/api/solver/Solver.java

@@ -52,7 +52,7 @@ public interface Solver<Solution_> {
      * {@link SolverEventListener#bestSolutionChanged(BestSolutionChangedEvent)} is often more appropriate).
      * <p>
      * This method is thread-safe.
-     * @return never null, but it can return the original, uninitialized {@link PlanningSolution} with a {@link Score} null.
+     * @return never null, but it can return the uninitialized {@link PlanningSolution} with a {@link Score} null.
      */
     Solution_ getBestSolution();
 
@@ -61,12 +61,22 @@ public interface Solver<Solution_> {
      * <p>
      * This is useful for generic code, which doesn't know the type of the {@link PlanningSolution}
      * to retrieve the {@link Score} from the {@link #getBestSolution()} easily.
+     * <p>
+     * This method is thread-safe.
      * @return null if the {@link PlanningSolution} is still uninitialized
      */
     Score getBestScore();
 
     /**
-     * @return the amount of millis spent between when this solver started (or last restarted) and ended
+     * Returns the amount of milliseconds spent solving since the last start.
+     * If it hasn't started it yet, it runs 0.
+     * If it hasn't ended yet, it returns the time between the last start and now.
+     * If it has ended already, it returns the time between the last start and the ending.
+     * <p>
+     * A {@link #addProblemFactChange(ProblemFactChange)} triggers a restart which resets this time.
+     * <p>
+     * This method is thread-safe.
+     * @return the amount of milliseconds spent solving since the last (re)start, at least 0
      */
     long getTimeMillisSpent();
 

optaplanner-core/src/main/java/org/optaplanner/core/impl/solver/DefaultSolver.java

@@ -109,11 +109,17 @@ public Score getBestScore() {
 
     @Override
     public long getTimeMillisSpent() {
+        Long startingSystemTimeMillis = solverScope.getStartingSystemTimeMillis();
+        if (startingSystemTimeMillis == null) {
+            // The solver hasn't started yet
+            return 0L;
+        }
         Long endingSystemTimeMillis = solverScope.getEndingSystemTimeMillis();
         if (endingSystemTimeMillis == null) {
+            // The solver hasn't ended yet
             endingSystemTimeMillis = System.currentTimeMillis();
         }
-        return endingSystemTimeMillis - solverScope.getStartingSystemTimeMillis();
+        return endingSystemTimeMillis - startingSystemTimeMillis;
     }
 
     @Override

optaplanner-core/src/main/java/org/optaplanner/core/impl/solver/scope/DefaultSolverScope.java

@@ -47,8 +47,8 @@ public class DefaultSolverScope<Solution_> {
      */
     protected Semaphore runnableThreadSemaphore = null;
 
-    protected Long startingSystemTimeMillis;
-    protected Long endingSystemTimeMillis;
+    protected volatile Long startingSystemTimeMillis;
+    protected volatile Long endingSystemTimeMillis;
 
     protected Score startingInitializedScore;