From 8c11d274fc75e0a393e716d43792b7912d3ac756 Mon Sep 17 00:00:00 2001
From: alejeune <aureliafacebook44@gmail.com>
Date: Wed, 5 Apr 2023 10:39:22 +0200
Subject: [PATCH] Added cycle detection and withdrawal

---
 .../java/jobshop/solvers/TabooSolver.java     | 52 ++++++++++++++++---
 1 file changed, 46 insertions(+), 6 deletions(-)

diff --git a/src/main/java/jobshop/solvers/TabooSolver.java b/src/main/java/jobshop/solvers/TabooSolver.java
index 6b23ecd..d09095a 100644
--- a/src/main/java/jobshop/solvers/TabooSolver.java
+++ b/src/main/java/jobshop/solvers/TabooSolver.java
@@ -8,10 +8,7 @@ import jobshop.encodings.Schedule;
 import jobshop.solvers.neighborhood.Neighborhood;
 
 import java.time.format.ResolverStyle;
-import java.util.Arrays;
-import java.util.Comparator;
-import java.util.List;
-import java.util.Optional;
+import java.util.*;
 
 public class TabooSolver implements Solver {
     final Neighborhood neighborhood;
@@ -32,6 +29,8 @@ public class TabooSolver implements Solver {
         Schedule schedule = baseSolver.solve(instance, deadline,randomness,randomRunNumber).get();
         ResourceOrder order = new ResourceOrder(schedule);
         ResourceOrder result = order;
+        // Create an array to store the cycle
+        ArrayList<Integer> historic = new ArrayList<Integer>();
 
         /*for output writing*/
         FileWriter fw = null;
@@ -82,9 +81,15 @@ public class TabooSolver implements Solver {
                             .toArray(ResourceOrder[]::new)[0];
                     result = order;
                 }
-                } catch (ArrayIndexOutOfBoundsException e2) { // no solution found ==> stop
-
+            } catch (ArrayIndexOutOfBoundsException e2) { // no solution found ==> stop
             }
+
+            /* Check if we have a cycle */
+            if (isCycle(historic, result.toSchedule().get())){
+                System.out.println("CYCLE");
+                break;
+            }
+
             System.out.println("\u001b[34m" + "Current makespam : " + result.toSchedule().get().makespan() + "\u001b[0m, "
                     + "\u001b[32m" + "Current best makespam : " + best + "\u001b[0m, "
                     + "\u001b[33m" + "Number of neighbours : " + getNumberOfNeighbours(neighbours) + "\u001b[0m, "
@@ -140,5 +145,40 @@ public class TabooSolver implements Solver {
         }
         return forbiddenNeighbours;
     }
+
+    private boolean isCycle(ArrayList historic, Schedule schedule){
+        historic.add(schedule.hashCode());
+        Boolean found = false;
+        Boolean result = true;
+        int indexCycle = 0;
+        int testTurtle = 0;
+        int testRabbit = 0;
+        if (historic.size() > 20) {
+            historic.remove(0);
+        }
+        int rabbit = 2;
+        for (int turtle = 1; turtle < (historic.size()/2) - 1; turtle ++){
+            if (historic.get(turtle) == historic.get(rabbit)){
+               indexCycle = turtle;
+               found = true;
+               testTurtle = turtle;
+               testRabbit = rabbit;
+               break;
+            }
+            rabbit = 2*turtle;
+        }
+        if (found){
+            for (int i = indexCycle; i < historic.size() - rabbit; i++)
+            if (historic.get(testTurtle) != historic.get(testRabbit)){
+                result = false;
+                testTurtle ++;
+                testRabbit ++;
+            }
+        }
+        if (result && found){
+            return result;
+        }
+        return false;
+    }
 }