diff --git a/src/main/java/de/dhbwstuttgart/typeinference/unify/TypeUnifyTask.java b/src/main/java/de/dhbwstuttgart/typeinference/unify/TypeUnifyTask.java
index 2d6dc8fa..d3ebe2c6 100644
--- a/src/main/java/de/dhbwstuttgart/typeinference/unify/TypeUnifyTask.java
+++ b/src/main/java/de/dhbwstuttgart/typeinference/unify/TypeUnifyTask.java
@@ -186,6 +186,12 @@ public class TypeUnifyTask extends RecursiveTask<Set<Set<UnifyPair>>>  {
 				usedTasks.cancel();
 				writeLog(nOfUnify.toString() + "cancel");
 				System.out.println("cancel");
+				try {
+					logFile.write("Abbruch");
+				}
+				catch (IOException e) { 
+					System.err.println("log-File nicht vorhanden");
+				}	
 			}
 			*/
 			rules = new RuleSet(logFile);
@@ -303,6 +309,11 @@ public class TypeUnifyTask extends RecursiveTask<Set<Set<UnifyPair>>>  {
 		/*
 		 * Step 1: Repeated application of reduce, adapt, erase, swap 
 		 */
+		synchronized (usedTasks) {
+			if (this.myIsCancelled()) {
+				return new HashSet<>();
+			}
+		}
 		
 		rekTiefe++;
 		nOfUnify++;
@@ -463,7 +474,11 @@ public class TypeUnifyTask extends RecursiveTask<Set<Set<UnifyPair>>>  {
 		//		.collect(Collectors.toCollection(HashSet::new));
 		//Muss auskommentiert werden, wenn computeCartesianRecursive ENDE
 		
-
+		synchronized (usedTasks) {
+			if (this.myIsCancelled()) {
+				return new HashSet<>();
+			}
+		}
 		
 		Set<Set<UnifyPair>> eqPrimePrimeSet = new HashSet<>();
 		
@@ -907,6 +922,11 @@ public class TypeUnifyTask extends RecursiveTask<Set<Set<UnifyPair>>>  {
 					writeLog("wait "+ forkOrig.thNo);
 					noOfThread--;
 					res = forkOrig.join();
+					synchronized (usedTasks) {
+						if (this.myIsCancelled()) {
+							return new HashSet<>();
+						}
+					}
 					//noOfThread++;
 					forkOrig.writeLog("final Orig 1");
 					forkOrig.closeLogFile();
@@ -922,6 +942,11 @@ public class TypeUnifyTask extends RecursiveTask<Set<Set<UnifyPair>>>  {
 					synchronized (this) {
 						noOfThread--;
 						Set<Set<UnifyPair>> fork_res = fork.join();
+						synchronized (usedTasks) {
+							if (this.myIsCancelled()) {
+								return new HashSet<>();
+							}
+						}
 						//noOfThread++;
 						writeLog("Join " + new Integer(fork.thNo).toString());
 						//noOfThread--; an das Ende von compute verschoben
@@ -1013,6 +1038,11 @@ public class TypeUnifyTask extends RecursiveTask<Set<Set<UnifyPair>>>  {
 					writeLog("wait "+ forkOrig.thNo);
 					noOfThread--;
 					res = forkOrig.join();
+					synchronized (usedTasks) {
+						if (this.myIsCancelled()) {
+							return new HashSet<>();
+						}
+					}
 					//noOfThread++;
 					forkOrig.writeLog("final Orig -1");
 					forkOrig.closeLogFile();
@@ -1028,6 +1058,11 @@ public class TypeUnifyTask extends RecursiveTask<Set<Set<UnifyPair>>>  {
 					synchronized (this) {
 						noOfThread--;
 						Set<Set<UnifyPair>> fork_res = fork.join();
+						synchronized (usedTasks) {
+							if (this.myIsCancelled()) {
+								return new HashSet<>();
+							}
+						}
 						//noOfThread++;
 						writeLog("Join " + new Integer(fork.thNo).toString());
 						//noOfThread--; an das Ende von compute verschoben 
@@ -1089,6 +1124,11 @@ public class TypeUnifyTask extends RecursiveTask<Set<Set<UnifyPair>>>  {
 		    		writeLog("wait "+ forkOrig.thNo);
 		    		noOfThread--;
 					res = forkOrig.join();
+					synchronized (usedTasks) {
+						if (this.myIsCancelled()) {
+							return new HashSet<>();
+						}
+					}
 					//noOfThread++;
 					forkOrig.writeLog("final Orig 2");
 					forkOrig.closeLogFile();
@@ -1103,6 +1143,11 @@ public class TypeUnifyTask extends RecursiveTask<Set<Set<UnifyPair>>>  {
 		    		synchronized (this) {
 		    			noOfThread--;
 						Set<Set<UnifyPair>> fork_res = fork.join();
+						synchronized (usedTasks) {
+							if (this.myIsCancelled()) {
+								return new HashSet<>();
+							}
+						}
 						//noOfThread++;
 						writeLog("Join " + new Integer(fork.thNo).toString());
 						//noOfThread--; an das Ende von compute verschoben