CMSC 433November 13th, 2007Homework 4• write test cases for BoundedAtomicQueue, using MultithreadedTC• Should be atomic, fair, and the correct size• You are given a correct implementation, and 4 broken implementations• Write test cases that distinguish them• Everything open, no release tests– this is a homework, not a project• Due Friday Nov 16th2Missing office hours• I’m going to miss almost of my office hours over through Nov 16th– various meetings, workshops and trips• Schedule for coming days– Tuesday, Nov 13th 10:45 - noon– Thursday, Nov 15th, noon-1:30pm3Upcoming stuff• WebGoat security homework• Distributed programming– Map/Reduce and Hadoop–4Project 3• Problem with submit server fixed– NoSuchMethodException• Some hints/suggestions5Making sure each node is visited just once• Absolutely wrong:– if (!visited.contains(n)) { visited.add(n); ... do computations for n; }• The Set.add method returns true if the add method caused something to be added to the set• If using Java 6, can use Collections.newSetFromMap(new ConcurrentHashMap<Node,Boolean>())6Creating work for a thread pool executor• Don’t use recursion to explore the graph• Rather, for each node that should be processed/examined,– create a Runnable to process that node– give it to a thread pool executor• If you have a recursive call, you are missing the point of the exercise7Exploring a graph8Can use FutureTask• This isn’t required, but you can use FutureTask to handle getValue requests– create a FutureTask for each node with a callable that invokes the compute method on the node– give the FutureTask to a thread pool executor– We don’t need to wait for these tasks to complete before returning from explore9Problem• explore method must not return until all nodes have been visited• No easy way to ask if a thread pool executor is done executing tasks• How are we going to handle this?10Pop ungraded
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