Computer Science Honours 2011

<H1>Computer Science Honours 2011</H1>

<H2>Distributed &amp; Parallel Processing<br>
Practical Two: JCSP</H2>

<H3>Bounded-Buffer Producer Consumer using Message Passing</H3>

<p>If you have not yet done so, first compile and run the <A HREF="SimplePC.zip">simple
Producer-Consumer program</A>,
using Java and the JCSP (Java Communicating Sequential Processes) library.&nbsp;
You can also download the <A HREF="jcsp1-0-rc4.jar">JCSP library here</A>.&nbsp; To install JCSP
simply type the following command using a command-line prompt: <CODE>jar xvf jcsp1-0-rc4.jar</CODE>.</p>

<P>For more details, refer to the <i><b>jcsp-docs</b></i> 
  document structure set up by the installation.&nbsp; See also the example code
  unpacked by the installation.&nbsp;
  Additional tutorial material on the JCSP package can also be downloaded from the JCSP website site
  <a href="http://www.cs.kent.ac.uk/projects/ofa/jcsp/" target="_blank">http://www.cs.kent.ac.uk/projects/ofa/jcsp/</a>.</P>

<P>You can also refer to a producer-consumer example 
  in a Java reference of your choice if you wish, but remember that you should 
  use the process creation structures of JCSP for this exercise, and not native 
  Java threads.</P>


<P>Once you have your own version of the Producer-Consumer program running, make the following modifications to it in
order:</P>

<OL>
  <LI>Add a buffer process to the system, which 
    runs concurrently with the producer and consumer, and which catches the output 
    of the producer, and passes it on to the consumer.
    
  <LI>Modify all 3 concurrent processes so that 
    they handle more than just one item.&nbsp; (Just use a loop to generate 100 integers 
    in the producer).&nbsp; The point of a buffer is that it should allow the rate of 
    production and consumption to be decoupled, so extend the buffer process to 
    store incoming items in a 10 element array.&nbsp;
    Remember that to allow the producer and 
    consumer to communicate with the buffer at their own convenience, the buffer 
    needs to include an <EM>alternative construct</EM>.&nbsp; See the <CODE>select</CODE> method 
    in the <CODE>Alternative</CODE> class.&nbsp; You will also need to cater for condition 
    synchronisation to avoid buffer underflow or overflow.
    
  <LI>Now that you have a working buffer to handle 
    one producer and one consumer, it should be a relatively simple task to add 
    one more of each kind of processor.&nbsp; Producer 1 should produce integers in 
    the range 1 to 100, and producer 2 in the range 101 to 200.&nbsp; The two consumers 
    should each consume 100 integers and display them on the console.&nbsp; Use 
    the same code for both Producers (passing a parameter to tell them what to 
    produce).

  <LI>Unless you have already been very careful 
    to keep count of the number of items produced, buffered, and consumed by each 
    concurrent process, you will find that your program hangs after it produces 
    its results and has to be interrupted with a CTRL-C.&nbsp; This is because one or 
    more processes has not terminated cleanly.&nbsp; Clean termination is not a compulsory 
    part of this assignment, but if you do add a mechanism to ensure that all 
    processes terminate cleanly at the end of the program, I will award a bonus 
    mark for it (counting up to 200 in the buffer process and then dying won't
    qualify for bonus marks &mdash; look for a general solution).
    
  <LI>What can you say about the tasking mechanism 
    of Java and JCSP from the patterns printed out by each consumer?
</OL>


<h3>To Hand In:</h3>

<P>You should submit a 
  copy of the bounded buffer with two producers and two consumers,
  with sample output and a short explanation of why the output patterns look the 
  way they do.</P>