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1. Assume that shared variable x is initially 0 and that threads T1 and T2 are as follows:...

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1. Assume that shared variable x is initially 0 and that threads T1 and T2 are as follows;T1 T2;x = x + 1, x = x - 1;What are the possible final values of x? (The statements are not inside critical sections.) Show your work.;2. Write a Java program with four threads. Your program should work as follows;- Each thread performs a simple task which is to output its thread ID, increment a shared variable named count, and display the;resulting value of count. Count is initalized to 0.;- The threads work in pairs. Threads 1 and 2 work as a pair, and Threads 3 and 4 work as a pair.;- The threads in each pair alternate peforming their task. That is, Thread1 performs its task first, then Thread2, then Thread1, then;Thread2, etc. Same for Threads 3 and 4 with Thread 3 going first.;- The thread pairs also alternate. That is, Thread pair 1 and 2 perform their tasks then Thread pair 3 and 4 perform theirs, then;Thread1 and Thread2, then Thread3 and Thread4, etc.;- The user enters on the command line the number of times that the threads should alternate. For example, if the user enters 2, each;thread in each pair performs its work twice, and each thread pair is given 2 chances to execute.;- At then end of execution, display the final value of shared variable count.;You must use counting semaphores to force your threads to alternate.;Sample output for: java Alternate 2;T1:1 // each of T1 and T2 performs its task 2 times, with T1 and T2 alternating;T2:2;T1:3;T2:4;T3:5 // then each of T3 and T4 performs its task 2 times, with T3 and T4 alternating;T4:6;T3:7;T4:8;T1:9 // then each of T1 and T2 performs its task 2 times, with T1 and T2 alternating;T2:10;T1:11;T2:12;T3:13 // then each of T3 and T4 performs its task 2 times, with T3 and T4 alternating;T4:14;T3:15;T4:16;count is 16;Sample output for: java Alternate 3;T1:1;T2:2;T1:3 // each of T1 and T2 performs its task 3 times, with T1 and T2 alternating;T2:4;T1:5;T2:6;T3:7 // then each of T3 and T4 performs its task 3 times, with T3 and T4 alternating;T4:8;T3:9;T4:10;T3:11;T4:12;T1:13 // a 2nd time for pair T1 and T2;T2:14;T1:15;T2:16;T1:17;T2:18;T3:19 // a 2nd time for pair T3 and T4;T4:20;T3:21;T4:22;T3:23;T4:24;T1:25 // a 3rd time for pair T1 and T2;T2:26;T1:27;T2:28;T1:29;T2:30;T3:31 // a 3rd time for pair T3 and T4;T4:32;T3:33;T4:34;T3:35;T4:36;count is 36;I created a template for you in file Alternate.java (attached). Complete this code by completing the run() methods for the threads and defining the necessary semaphores.;The Java countingSemaphore and TDThread classes are in a Java jar file, which can be found in the following zip file;http://www.cs.gmu.edu/~rcarver/ModernMultithreading/ModernMultithreadingJavaJar.zip;Class countingSemaphore has operations P() and V() (instead of the acquire() and release() operations, respectively, used in textbook.);The Zip file also contains some directories with sample programs, see the directories with "Semaphores" in their names.;Assuming the jar file is in the same directory as your Alternate.java file;Compile your program using;Windows: javac -classpath.,ModernMultithreading.jar Alternate.java;Unix: javac -classpath.:ModernMultithreading.jar Alternate.java;Run your program using;Windows: java -classpath.,ModernMultithreading.jar Alternate 2 // choose 2 or some other number of iterations;Unix: java -classpath.:ModernMultithreading.jar Alternate 2;If you are having deadlock problems, it may help to run your program with deadlock detection turned on;Windows: java -classpath.,ModernMultithreading.jar -Dmode=trace -DdeadlockDetection=on Alternate 2;Unix: java -classpath.:ModernMultithreading.jar -Dmode=trace -DdeadlockDetection=on Alternate 2;Deadlock detection will provide helpful debugging information about the cuase of the deadlock. To make this information more readable, it helps to name your semaphores when you create them;countingSemaphore mutex = new countingSemaphore(1,"mutex"), // initial value is 1, name is "mutex;The name you supply will be used to identify your semaphore in the debug messages.

 

Paper#73575 | Written in 18-Jul-2015

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