fix: only call RNG in Tabu search when necessary

Author: triceo

core/src/main/java/ai/timefold/solver/core/impl/localsearch/decider/acceptor/tabu/AbstractTabuAcceptor.java

@@ -143,8 +143,8 @@ public boolean isAccepted(LocalSearchMoveScope<Solution_> moveScope) {
             return false;
         }
         var acceptChance = calculateFadingTabuAcceptChance(tabuStepCount - workingTabuSize);
-        var accepted = moveScope.getWorkingRandom().nextDouble() < acceptChance;
-        if (accepted) {
+        var accepted = isAccepted(moveScope, acceptChance);
+        if (isAccepted(moveScope, tabuStepCount)) {
             logger.trace("{}        Proposed move ({}) is fading tabu with acceptChance ({}) and is accepted.",
                     logIndentation,
                     moveScope.getMove(), acceptChance);
@@ -156,6 +156,26 @@ public boolean isAccepted(LocalSearchMoveScope<Solution_> moveScope) {
         return accepted;
     }
 
+    /**
+     * @param fadingTabuStepCount {@code 0 < fadingTabuStepCount <= fadingTabuSize}
+     * @return {@code 0.0 < acceptChance < 1.0}
+     */
+    private double calculateFadingTabuAcceptChance(int fadingTabuStepCount) {
+        // The + 1's are because acceptChance should not be 0.0 or 1.0
+        // when (fadingTabuStepCount == 0) or (fadingTabuStepCount + 1 == workingFadingTabuSize)
+        return (workingFadingTabuSize - fadingTabuStepCount) / ((double) (workingFadingTabuSize + 1));
+    }
+
+    private boolean isAccepted(LocalSearchMoveScope<Solution_> moveScope, double acceptChance) {
+        if (Double.compare(acceptChance, 0.0d) <= 0) {
+            return false;
+        } else if (Double.compare(acceptChance, 1.0d) >= 0) {
+            return true;
+        }
+        // Only affect the RNG when we actually need to.
+        return moveScope.getWorkingRandom().nextDouble() < acceptChance;
+    }
+
     private int locateMaximumTabuStepIndex(LocalSearchMoveScope<Solution_> moveScope) {
         var checkingTabus = findTabu(moveScope);
         var maximumTabuStepIndex = -1;
@@ -183,16 +203,6 @@ private int locateMaximumTabuStepIndex(LocalSearchMoveScope<Solution_> moveScope
         return maximumTabuStepIndex;
     }
 
-    /**
-     * @param fadingTabuStepCount {@code 0 < fadingTabuStepCount <= fadingTabuSize}
-     * @return {@code 0.0 < acceptChance < 1.0}
-     */
-    protected double calculateFadingTabuAcceptChance(int fadingTabuStepCount) {
-        // The + 1's are because acceptChance should not be 0.0 or 1.0
-        // when (fadingTabuStepCount == 0) or (fadingTabuStepCount + 1 == workingFadingTabuSize)
-        return (workingFadingTabuSize - fadingTabuStepCount) / ((double) (workingFadingTabuSize + 1));
-    }
-
     /**
      * @param moveScope
      * @return some tabu lists allow null, some don't; children will override