Re: JCSP - Interpreter (& too restricted visibility of classes in JCSP package)

[Anne van Rossum <anne@xxxxxxxxxxx>]

Hi Kevin,

Thanks for your response. The code from One2OneChannelImpl can not be
copied, because it uses the method .schedule() from the Alternative
class in the .util package that is not visible outside that package.

I want to have different classes of components. Let I use the following
terminology:
      * CodeBlocks: implement CSProcess but send and receive "normal"
        data over their channel inputs and outputs;
      * Interpreters: implement CSProcess and may send and receive
        CodeBlock's over their channel inputs and outputs. Interpreters
        therefore are able to schedule, manipulate CodeBlock's. In this
        way e.g. different scheduling techniques can be tried in
        parallel. Or  interpreters may only understand CodeBlock's in a
        certain programming language. They function as virtual machines;
      * Universal Interpreters: implement (in Java) CSProcess and may
        send and receive Interpreters over their channel inputs and
        outputs. Channel's should cross-language and cross-platform in
        the sense of pipes, CORBA, tcp/ip. Transporting an interpreter
        to another machine corresponds with e.g. downloading a JRE to
        that machine. They are a kind of "universal" virtual machines.

CodeBlock's have certain restrictions on their channel inputs that I
address explicitely. 

I will temporarily remove the extension of the AltingChannelInput class.

That channel endpoints are separate entities is indeed useful. They are
in other Java libraries modelled as InputPipe and OutputPipe (JXTA), as
SourceChannel and SinkChannel (java.nio.channels), as Puttable and
Takable (java.util.concurrent).

Kind regards,

Anne

On Tue, 2007-01-09 at 17:16 +0000, Kevin Chalmers wrote:
> Hi Anne,
> 
> In Peter Welch's original JCSP library, the channel objects where much 
> more accessible.  This does however lead to problems.  As an example, 
> consider I receive an object from a channel and then need to check if it 
> is either a ChannelInput or ChannelOutput object.  In Peter's library, 
> both of these where the case, and this led to problems in the usage on 
> the JCSP.net library, so Quickstone modified the model somewhat.  
> Therefore the channel ends are each distinct objects from the channel 
> itself.
> 
> Now, as for your problem, I suggest simply copying the 
> One2OneChannelImpl code into a new class (One2OneProcChannel) and then 
> use it instead.  Ensure the channel extends AltingChannelInput (is 
> therefore guarded and can be used in an Alternative), ChannelOutput and 
> One2OneChannel.  This class will therefore be a One2OneChannel as the 
> original, but will allow you to do your modifications.  The interface 
> model in JCSP is sufficiently strong to allow this to be fairly routine.
> 
> As for the requirement of what you want to do, I am not clear.  Normal 
> channels will quite happily carry a CSProcess (everything in Java is an 
> object except primitive data), and the in() and out() methods of 
> One2OneChannelImpl already return this as a result, the channel being 
> both an input and output.  If you could clear up the major difference I 
> may be able to help further.
> 
> Regards
> 
> Kevin Chalmers
> Research Student
> Napier University
> Edinburgh
> 
> Anne van Rossum wrote:
> > Dear list members,
> >
> > The JCSP library is nice. However, for my purposes there is too much
> > package protected. Is this for some reason? 
> >
> > I am creating a special CSProcess, let I call it an Interpreter. The
> > Interpreter is decoupled from the application functionality (e.g. it
> > does have several processes in an array). The Interpreter may take care
> > of other non-functional aspects:
> >       * Scheduling: The ParallelInterpreter does have a run() method
> >         that calls all its processes in a Parallel construct. Other
> >         interpreters may implement all kind of pool policies. The
> >         Interpreter can be called a Pool in this scenario;
> >       * Coupling: Instead of containing an CSProcess array, the
> >         interpreter may access a pool where processes swim around. It
> >         can take one that performs fast of about which it has positive
> >         experiences;
> >       * Process manipulation: An Interpreter may consider its processes
> >         and combine them too one new process, before running it:
> >         Transforming channels to (variable) assignments within the same
> >         namespace;
> >
> > To create an Interpreter I want to have ChannelInput's and
> > ChannelOutput's that carry CSProcess instances. Let I call them
> > ChannelProcInput's and ChannelProcOutput's. So, the
> > One2OneProcChannelImpl should implement ChannelProcInput,
> > ChannelProcOutput and One2OneProcChannel. The methods to overwrite are
> > only in() and out(): 
> >   public ChannelProcInput in() { return this(); }
> >   public ChannelProcOutput out() { return this(); } //and read, write
> > Regretfully One2OneChannelImpl is package-protected, so I can't extend
> > it. Neither can I copy its code, because the method schedule of the
> > Alternative class is not visible either.
> >
> > Can the visibility be adapted? Or should I create my adapted jcsp
> > library? In that case I need at last the source code of the
> > com.quickstone.jcsp.util library. Thanks in advance!
> >
> > Kind regards,
> >
> > Anne
> >
> > On Tue, 2007-01-02 at 10:38 +0100, Anne van Rossum wrote:
> >   
> >> Dear list members,
> >>
> >> Currently I am playing with the JCSP library. I wrote this code that has
> >> a Writer that writes values on channelA, an Incrementer that increments
> >> those values and a Reader that reads them and displays them at the
> >> console:
> >>
> >> Code:
> >> public static void main(String[] args) {
> >>     ChannelFactory channelFactory = new StandardChannelFactory();
> >>     One2OneChannel channelA = channelFactory.createOne2One();
> >>     One2OneChannel channelB = channelFactory.createOne2One();
> >>    
> >>     Parallel processPool = new Parallel(
> >>       new CSProcess[] {
> >>           new Writer(channelA.out()),
> >>           new Incrementer(channelA.in(), channelB.out()), 
> >>           new Reader(channelB.in())
> >>       }
> >>     );
> >>
> >>     processPool.run();
> >>   }
> >>
> >> Questions:
> >> I have the following questions regarding this example:
> >> * The CSProcesses run parallel, but it is unclear how each process gets
> >> its processing time. Maybe the Reader gets much more cycles than the
> >> Writer. Who knows?
> >> * The CSProcesses may be placed in any order. The Incrementer can not
> >> read a value from its input channel when it is not available. How is
> >> this implemented? Is the Incrementer polling channelA? Or send channelA
> >> an event to the Incrementer?
> >> * The nomenclature of channel.in() and channel.out() is confusing.
> >> Channel.out() should be the endpoint of the channel, not the output of
> >> the component where a channel starts. If a channel is a first-class
> >> entity, it should be treated like that.
> >> * The Parallel construct is rigid. Why is it not coupled to some kind of
> >> "parallel" thread pool (or actually a process pool)? The implementation
> >> of above gives all processes (supposedly) the same amount of processing
> >> time in parallel. An "alternative" construct is also allowed. And some
> >> implementing "priorities". That's it. How can I code other process pools
> >> with other policies?
> >> * On rewiring the network the One2OneChannel object has to be replaced
> >> by an Any2OneChannel object or One2AnyChannel object, etc. How can a
> >> process removed easily? There is a Parallel.removeProcess method that
> >> will be executed before a call to run(). The Reader process above reads
> >> continuously from channelB and never stops. How can I swap the Writer
> >> for another in that case? Code after processPool.run() will not be
> >> reached.
> >> * How many threads are there actually? Has every channel, or every
> >> "plug" of a channel their own thread? Or only the CSProcess objects?
> >>
> >> Background:
> >> What do I have in mind? I like to develop large-grain dataflow model
> >> where the large-grain processes are aggregations of small-grain
> >> processes (and have a better performance). If such a conversion (from
> >> small to large-grain processes) can be automated, software will
> >> automatically adjust to the amount and type of hardware processors
> >> (multiple CPUs, FPGAs, etc.) 
> >> For that:
> >> * Different CSProcesses should be implemented;
> >> * Those should be swapped for each other easily;
> >> * Those should be compared w.r.t. performance;
> >> * Aggregations of CSProcesses should be compared with the distinct
> >> CSProcesses w.r.t. performance;
> >> * Channels should be plugged somewhere else easily.
> >> Etc. etc.
> >>
> >> Thanks a lot in advance for taking time!
> >>
> >> Kind regards,
> >>
> >> Anne
> >>
> >>     
> >
> >   
> 
> 
> 
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