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Re: Transputer - schools

Hi Ian,

It might be of value for you to cobble up two or three examples where "prioritised vectored interrupts" give a clear advantage over round-robin interrupts (which is what PRI PAR amounts to). The advantage has to be clear, because of the price paid in priority inversions. It always seemed to me that round-robin interrupts were enough to give the required response in most problems - unless you did not have enough hardware. And Transputer-style PRI PAR can be implemented on any embedded chip that offers interrupts.

Larry

On Jun 29, 2013, at 11:05 AM, Ian East <ian.east@xxxxxxxxxxxx> wrote:

Hi David

I'd be very interested in anything new you intend regarding reactive (event-driven) behaviour and prioritisation.

A clear understanding of programming prioritisation in a CPA (process-oriented) language still seems to be lacking (though Bill Roscoe's recent book has a little more on the subject), yet it still seems to me to be a necessary element in a "model for abstraction".

For me, this was the one disappointment in the box of delight that was occam.  (I had grown used to relying on prioritised vectored interrupts and wanted something similar.)

I know you can achieve almost anything in practice now simply by defining dedicated additional processes, and perhaps processors, but still believe that a PL should afford _expression_ of these things.

Ian

On 29 Jun 2013, at 18:41, David May <dave@xxxxxxxxxxxxxxxxxxxxx> wrote:

I am working on putting concurrency into X - this will
be slightly different from occam (reflecting what I have
learned over the last few years). 

From an educational viewpoint, X is interesting for 
several reasons:

1. It is small and understandable - both language and 
    compiler

2. It is powerful enough to express its own compiler

3. It has no GOTOs, Breaks, Pointers etc - I think 
    Floyd-Hoare logic can be used on any program 
    you can write in X. 




Ian East
57, Kidlington Road, Islip, Oxfordshire OX5 2SS
(+44) 0 1865 373268