Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!ames!lll-lcc!lll-winken!uunet!munnari!murtoa.cs.mu.oz.au!ditmela!latcs1!suter
From: suter@latcs1.oz (David Suter)
Newsgroups: comp.sys.transputer
Subject: transputer scheduler
Keywords: priority
Message-ID: <5339@latcs1.oz>
Date: 25 Mar 89 06:45:38 GMT
Organization: Comp Sci, La Trobe Uni, Australia
Lines: 35

I have found little information about the implementation of concurrent processes
on a single transputer. At the hardware level the Transputer Ref. Manual makes
the point that the microcoded scheduler itself does not consume time
as inactive (read for i/o or suspended for a specified time) processes do not 
consume processor time. They are, it seems,  suspended
and placed on the active list only when an autonomous link interface (for i/o
- for timer in case of specified time?) cuases them to be rescheduled. 
A process is executed until it requests i/o or awaiting the timer.

This seems fine, however there is little information about how the OCCAM 
compiler maps its concurrent processes onto this. There is a brief statement
about PRIoritised processes - but what about equal priority processes. Does
the current implementation(s) of OCCAM time slice the equal priority
proceses (if so at what rate) or does it follow the above hardware model for
efficiency where
PAR
  process1
  process2
will actually run either as SEQ process1,process2 or visa versa
if neither requires i/o.
It seems hard to reason about efficiency of code without this info - can anyone
point me to a detailed account of this.
Also - what about the various C compilers - do any of them support 
multiprocessing on a single transputer - if so how?


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