CSC 543 Multiprocessing & Concurrent Programming, Fall 2016

Transcription

1 CSC 543 Multiprocessing & Concurrent Programming, Fall 2016 Dr. Dale E. Parson, Midterm Exam Project, Assorted Thread Synchronization Problems This assignment is due by 11:59 PM on Wednesday November 2 via make turnitin. Perform the following steps to set up this project and to get my handout. Start out in your login directory on csit (a.k.a. acad). cd $HOME/multip cp ~parson/multip/prisonerdmidterm2016.problem.zip prisonerdmidterm2016.problem.zip Then log into ONE of the following machines via the ssh command from csit. ssh hermione ssh dumbledore ssh luna ssh harry My advice is to do your development and testing on one of the Linux machines the per-context speed is greater and then do additional testing on harry. Always run make test on one of these machines (gmake test on harry) before running make turnitin on a Linux machine to ensure that last-minute edits or file transfers have not created problems. After logging into one of the above machines, do the following. cd./multip unzip prisonerdmidterm2016.problem.zip cd./prisonerdmidterm2016 gmake test_atomic test_semaphore Those two tests should pass. They use these source files from assignment 2. PrisonerTest.java Tables.java PlayerAtomic.java PlayerSemaphore.java # NO CHANGES NEEDED FOR EXAM # CHANGES NEEDED FOR EXAM # SAME AS PlayerExplicit.java, CHANGES NEEDED # SAME AS PlayerExplicit.java, CHANGES NEEDED 1. Tables.java is back to the starting point for assignment 2, i.e., it is not thread safe or immutable because it exposes several java.util.hashmap objects in the penalty field to multithreaded access. Here are the STUDENT instructions from within Tables.java. * STUDENT: MIDTERM: * This is my starting point for assignment 2's Tables.java. * It uses non-thread-safe java.util.hashmap for its * Map objects. You must continue to use java.util.hashmap * -- DO NOT CHANGE java.util.hashmap IN ANY WAY -- * but you must make this class thread safe for multi-threaded * access using some other means. ADD A COMMENT HERE EXPLAINING * YOUR SOLUTION (You can use any package as you see fit * within this source file.): page 1

2 2. PlayerAtomic.java has identical code to my solution PlayerExplicit.java that uses an explicit Reentrant lock and condition variable. Only the class name has changed. It works correctly. However, you must modify it as explained in its STUDENT comments: * PlayerAtomic plays the Iterated Prisoner's Dilemma with its * partner using an explicit lock & condition variable which a * STUDENT must change to using one or more object or objects from one or more classes * in package java.util.concurrent.atomic. THERE MUST BE NO OBJECTS * FROM CLASSES IN PACKAGE java.util.concurrent.locks IN THIS CLASS, * AND THERE MUST BE NO USE OF IMPLICIT OR EXPLICIT LOCKS OR * CONDITION VARIABLES. STUDENTS MUST MAKE THIS WORK USING ATOMICS. After you replace all uses of the explicit lock and condition variable with one or more atomic objects from package java.util.concurrent.atomic, gmake test_atomic should work correctly, without diffs or hanging. 3. PlayerSemaphore.java has identical code to my solution PlayerExplicit.java that uses an explicit Reentrant lock and condition variable. Only the class name has changed. It works correctly. However, you must modify it as explained in its STUDENT comments: * PlayerSemaphore plays the Iterated Prisoner's Dilemma with its * partner using an explicit lock & condition variable which a * STUDENT must change to using one or more objects from class * java.util.concurrent.semaphore. * THERE MUST BE NO OBJECTS FROM CLASSES IN PACKAGE * java.util.concurrent.atomic IN THIS CLASS, * AND THERE MUST BE NO USE OF IMPLICIT OR EXPLICIT LOCKS OR * CONDITION VARIABLES. STUDENTS MUST MAKE THIS WORK USING ONE OR * MORE SEMAPHORE OBJECTS. After you replace all uses of the explicit lock and condition variable with one or more Semaphore objects from package java.util.concurrent, gmake test_semaphore should work correctly, without diffs or hanging. 4. This part of the assignment, derived from assignment 1, relates to the following source files, and can be tested by using make test_pipeline. BigDecimalPipelineBuilder.java PipelineStage.java PipeSourceRandom.java PipeStageMath.java PipeSinkFile.java The last three files in bold are the files that you might have to change. Instructions are in file testscript, which you must NOT change. # STUDENT ASSIGNMENT FOR MIDTERM "make test_pipeline" portion: # The first "true true" test run below works OK -- It is multi-threaded # and blocking. The second test that uses non-blocking multi-threading hangs. # Your assignment is to analyze why the second test line hangs, and then # to change a SUBSET of the non-blocking calls WITHIN THE SCOPE OF THE page 2

3 # if (inputmidtermq!= null) { # AND/OR # if (outputmidtermq!= null) { # in the three pipeline classes PipeSinkFile.java, # PipeSourceRandom.java, and/or PipeStageMath.java, to use # blocking Queue calls. At least one Queue call within these "if" blocks # must be non-blocking, and at least one call must be blocking. # Write within a comment in the files in which you make changes, # 1. WHY USING ALL-NON-BLOCKING CALLS HANGS, and also # 2. WHY YOUR MIX OF BLOCKING AND NON-BLOCKING CALLS WORKS CORRECTLY. runatest true true java.util.concurrent.synchronousqueue runatest true false java.util.concurrent.synchronousqueue Here are the initialization statements for inputmidtermq and outputmidtermq in the files in which they appear: // The next statement says that if inq is in fact a // blocking queue, then set inputmidtermq to that, // else to null. BlockingQueue<BigDecimal []> inputmidtermq = (inq instanceof BlockingQueue)? ((BlockingQueue<BigDecimal []>) inq) : null ; // The next statement says that if ouq is in fact a // blocking queue, then set outputmidtermq to that, // else to null. BlockingQueue<BigDecimal []> outputmidtermq = (ouq instanceof BlockingQueue)? ((BlockingQueue<BigDecimal []>) ouq) : null ; Therefore, the if (inputmidtermq!= null) { and if (outputmidtermq!= null) { code blocks to consider for modification are BlockingQueue object references passed to the pipeline stage as plain Queue object references. Keep these if statement lines unchanged, but consider changing the Queue method calls within those blocks to BlockingQueue blocking calls; but you must keep at least one or more of the calls non-blocking; for the non-blocking calls you can use either the exception-throwing or the flag-returning non-blocking calls. Add comments where you make changes that explain the reason for the original problem, and also why your change or changes fix the problem. Here is a test run on the handout code. I am hitting control-\ after the test hangs. Control-\ (control backslash) causes the JVM to show stack traces. $ make test_pipeline /bin/rm -f sink.ref ln -s ~parson/tmp/sink.ref./sink.ref chmod +x testscript STUDENT=parson bash -x././testscript + runatest true true java.util.concurrent.synchronousqueue + CLASSPATH=..:jcip-annotations.jar + time java prisonerdmidterm2016.bigdecimalpipelinebuilder true true prisonerdmidterm2016.pipesourcerandom ' ' java.util.concurrent.synchronousqueue prisonerdmidterm2016.pipestagemath + java.util.concurrent.synchronousqueue prisonerdmidterm2016.pipesinkfile /home/kutztown/parson/tmp/parsonsink.out page 3

4 There are 64 contexts on this machine. RUNNING java prisonerdmidterm2016.bigdecimalpipelinebuilder true true prisonerdmidterm2016.pipesourcerandom java.util.concurrent.synchronousqueue prisonerdmidterm2016.pipestagemath + java.util.concurren t.synchronousqueue prisonerdmidterm2016.pipesinkfile /home/kutztown/parson/tmp/parsonsink.ou t CPU TIME FOR PipeSourceRandom = , USER TIME = CPU TIME FOR PipeStageMath = , USER TIME = CPU TIME FOR PipeSinkFile = , USER TIME = ELAPSED = 9.345, TOTAL CPU = , USER CPU = , SYSTEM CPU = real 10.0 user 16.1 sys exitstatus=0 + chmod 666 /home/kutztown/parson/tmp/parsonsink.out + ln -s /home/kutztown/parson/tmp/parsonsink.out./sink.out ln: cannot create./sink.out: File exists + '[' 0 -ne 0 ']' + diff./sink.out /home/kutztown/parson/tmp/sink.ref + exitstatus=0 + '[' 0 -ne 0 ']' + /bin/rm -rf /home/kutztown/parson/tmp/parsonsink.out./sink.out + runatest true false java.util.concurrent.synchronousqueue + CLASSPATH=..:jcip-annotations.jar + time java prisonerdmidterm2016.bigdecimalpipelinebuilder true false prisonerdmidterm2016.pipesourcerandom ' ' java.util.concurrent.synchronousqueue prisonerdmidterm2016.pipestagemath + java.util.concurrent.synchronousqueue prisonerdmidterm2016.pipesinkfile /home/kutztown/parson/tmp/parsonsink.out There are 64 contexts on this machine. RUNNING java prisonerdmidterm2016.bigdecimalpipelinebuilder true false prisonerdmidterm2016.pipesourcerandom java.util.concurrent.synchronousqueue prisonerdmidterm2016.pipestagemath + java.util.concurren t.synchronousqueue prisonerdmidterm2016.pipesinkfile /home/kutztown/parson/tmp/parsonsink.ou t The process hangs. Here are the stack traces for the three pipeline threads after hitting control-\. "Thread-2" prio=3 tid=0x002ba400 nid=0x26 runnable [0xb537f000] at java.util.concurrent.synchronousqueue.poll(synchronousqueue.java:888) at prisonerdmidterm2016.pipesinkfile.run(pipesinkfile.java:98) at java.lang.thread.run(thread.java:619) "Thread-1" prio=3 tid=0x002b8c00 nid=0x25 runnable [0xb547f000] at java.util.concurrent.synchronousqueue.poll(synchronousqueue.java:888) at prisonerdmidterm2016.pipestagemath.run(pipestagemath.java:112) page 4

5 at java.lang.thread.run(thread.java:619) "Thread-0" prio=3 tid=0x002b7800 nid=0x24 runnable [0xb557f000] at prisonerdmidterm2016.pipesourcerandom.run(pipesourcerandom.java:106) at java.lang.thread.run(thread.java:619) The threads are always either in a non-blocking call to a SynchronousQueue object, or in a polling loop, depending on when control-\ is hit. Here is the code in the neighborhood of PipeSourceRandom.java:106: 105 if (outputmidtermq!= null) { 106 while (! outputmidtermq.offer(result)) { 107 // spin until the blockqueue accepts the value 108 } 109 } else if (ouq!= null) { 110 ouq.add(result); 111 } else { 112 oubq.put(result); 113 } Once you have make test_pipeline working, make clean test should work, passing all tests without hanging. Make sure to write documentation comments explaining the problem and why your solution fixes it for this last part of the exam. When you are done working, run make turnitin to turn the assignment in by the deadline. page 5