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C++ Agents Implementation

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  1. C++ Agents Implementation Chris Rouse CSS 497

  2. Outline • Finish Agent Implementation • Involves changes to the following classes: • Agents_base.h/.cpp • Agent.h/.cpp • Mprocess.h/.cpp • Messages.h/.cpp • Exchange_helper.h/.cpp • Attempt to fix Eclipse IDE development problems for C++ version

  3. Agents_base.h/.cpp • Must add methods: • CallAll() • Instantiate bag of Agents to use • Must allocate Agents for each thread • Will send a command to all agents to execute • Wait for response back • ManageAll() • Will need to update information between all agents • Manages spawning, migrating, and killing of agents

  4. Agents_base.h/.cpp cont. • Difficulties: • All must pull from a single bag, causing a possibility for race conditions • This leads to the bag of agents being a critical section Normal Wiki example Race Condition • To remedy the problem, we need to make use of pthread_mutex_lock() to control when a thread can access this bag

  5. Agents_base.h/.cpp • Mutex locking will help prevent race conditions by ‘locking down’ the critical section upon use • Any requests mustfirst acquire the lockrights before they canaccess the agents • If bag is already locked,other requests mustwait until the lock releases and notifyAllis called before attempting to gain thelock again

  6. Agents_base.h/.cpp • Difficulties cont: • Waiting and Notifying • Should wait to hear back about status of agent • Typically we make use of Notifyand Wait • Can use provided methods barrierThreads and resumeThreads to wait and notify • What to do when an Agent doesn’t send notifications back? • At this time, we will assume that all Agents will respond and not take precautions in the event they do not • As currently planned, if an Agent doesn’t respond, the program will simply crash

  7. Agents_base.h/.cpp • CallAll method will essentially work like so: Step 1:Create Bag of Agents Step 2:Lock Bag Upon First Pop Request Step 3:Remove Last AgentFrom Vector of Agents Step 4:Send Copy of Commandto Popped Agent Step 7:Wait for Agentsto Finish Task Step 8:Collect Finished Agents into New Bag and Replace Old Bag Step 5:Release the Lock Step 6:Continue UntilOut of Agents

  8. Agents.h/.cpp • Must add methods: • Spawn() • To create Agents in current place • Migrate() • To move agents between Place locations • Kill() • To remove an Agent when it is finished with execution • This must also handle sending the commands to the slave agents

  9. Messages.h/.cpp & Exchange_helper.h/.cpp • Messages will need to be modified: • This will need to use the CallAll() & ManageAll() calls mentioned earlier • Exchange_helper will need to be modified too • Will need to be able to exchange agents between slaves • This will happen either locally in the same place or through a set of slave locations

  10. Current Status • Still working on CallAll() method • Reading and understanding existing code has been time consuming and confusing • Working on recompilation of existing code using Makefile while on campus • Decided to use a single bag of Agents to more efficiently handle race condition vs. Multiple bags of Agents • Working on implementing tests to make sure Agents are being taken correctly and passed correct instructions • Wait and Notify have not been used and tested yet

  11. Current Difficulties • Unfamiliar code • Code is complex and often contains information that I don’t understand • No working IDE • Eclipse has issues with some of the function calls and classes • Currently working on fixing problems that would prevent IDE development of the C++ version • Unknown behavior • Haven’t worked with the code’s output much yet, so any output I read needs to be checked for correct behavior, then rechecked with new changes • Code must be recompiled on campus • Code uses libraries stored in Professor Fukuda’s campus drive, so to recompile easily, needs to happen via SSH or on campus computers

  12. Deprecation Fixes • Some functions in the code are now deprecated and throw errors when used • Most recent example is bcopy(), which is now deprecated in newer Linux systems • My original fix was to include the String.h class, which had many of the deprecated values still included in it • This call can now be made using the memcpy() call, which takes the same parameters as bcopy, and functions the same • My current copy of the code contains all changes made for bcopy using a quick Linux ‘find | xargs | sed’ command to make all the necessary replacements, though no testing as of yet

  13. Future Plans • Finish wait/notify in Agents_base and check for errors • Test the memcpy command to make sure it works as intended • Fully test CallAll implementation • Move onto Spawn and Kill methods of Agents when complete with all the above • Continue to work on Eclipse IDE problems to enable further development easier for new research students