Re: Teaching Concurrency

[mph@oberon.inmos.co.uk (Mike Harrison)]

In article <33100@watmath.waterloo.edu> sccowan@watmsg.waterloo.edu (S. Crispin Cowan) writes:
>When to use tasking critically depends on the cost of the tasking
>operations.


Not necessarily so!

There are different possible goals in writing a program, run-time efficiency
is only one, another may be 'write-time' efficiency.

Ada tasking is, (in addition to permitting an implementation to allow the
use of multi-processor systems), an abstraction mechanism for the convenient
expression of concurrency. If a user can express his needs more easily and
effectively using tasking constructs, he may not be (seriously) concerned
about the running speed of the program.

For example, in a previous job, I had to write simulation of the behaviour 
of a multi-processor system (in executing Ada tasking as it happens), using
1, 2, 3 or 4 cpus.
It was much easier to represent the processors as separate tasks and to use
redzvous to simulate interactions than to write a single serial program with
explicit handling of the (simulated) paralellism.

However, I didn't care if the program took twice as long to run.


Mike.


Michael P. Harrison - Software Group - Inmos Ltd. UK.
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