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Paper Details

  title = "{A}n occam {M}odel of {XCHAN}s",
  author= "Welch, Peter H.",
  editor= "Welch, Peter H. and Barnes, Frederick R. M. and Broenink, Jan F. and Chalmers, Kevin and Pedersen, Jan Bækgaard and Sampson, Adam T.",
  pages = "329--330",
  booktitle= "{C}ommunicating {P}rocess {A}rchitectures 2013",
  isbn= "978-0-9565409-7-3",
  year= "2013",
  month= "nov",
  abstract= "Øyvind Teig, in ''XCHANs: Notes on a New Channel Type'',
     proposed a higher level channel construct (XCHAN) that
     attempts to reconcile those wedded to asynchronous message
     passing with the synchronous form in CSP. Sending a message
     does not block the sender, but the message may not get sent:
     the sender receives a success/fail result on each send. The
     XCHAN provides a conventional feedback channel on which
     it signals when it is ready to take a message. Being ready
     means that it has space (if it is buffered) or a reading
     process has committed to take the message (if it is not
     buffered). Sending to a ready XCHAN always succeeds;
     sending to an XCHAN that is not ready always fails. The
     sender can always wait for the signal from the XCHAN
     (whilst ALTing on, and processing, other events) before
     sending. We can model an XCHAN by a process in occam-pi.
     Buffered XCHANs are easy. Zero-buffered XCHANs are a little
     harder, because we need to maintain end-to-end
     synchronisation. However, occam-pi's extended input
     (??) and output (!!) primitives enable the process
     implementing the XCHAN to be hidden from its users.
     Unfortunately, extended outputs are not yet in the language,
     but their semantics can be simulated by making the receiving
     process read twice and ignore the first (which is just
     a signal whose taking must commit the reader to its second
     read). An important message is that sane higher level
     synchronisation mechanisms are usually not hard to implement
     efficiently via the low level CSP primitives offered by
     occam-pi. Although not yet measured for XCHANs, it is
     likely that such simulation in occam-pi will have
     competitive performance with direct implementation

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