Re: SDL-News: a problem about SDL instance

Subject: Re: SDL-News: a problem about SDL instance
From: Rick Reed TSE (
Date: Fri Jul 14 2000 - 18:18:34 GMT

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Bi Hai at wrote on 14/07/2000 04:14:

> In one BLOCK, there are many instances of a PROCESS. These instances
> communicate with other instances of another different fuction BLOCK using the
> same Primitive. How can the instance in one BLOCK distinguish its associated
> instance in another BLOCK so that the signal can communicate only between each
> other and not to other intances?

I am not sure that I fully understand the question, so I will first re-state
what I think the requirement is:

One block contains a number (n) of instance of process X and another block
contains the same number of instance of process Y. An X process instance
always communicates with the same Y process instance and vice versa.

In SDL this can be achieved by a scheme similar to the one I outlined in the
reply to <> today.

However, Bi Hai states that the requirement is for a protocol, so perhaps
the reality is the two blocks are actually at two end of the protocol and
therefore it is no realistic to expect an SDL Pid to be transmitted end to
end. In this case, there would normally be a unique index passed over the
protocol. At the receiving end the protocol signal would be received by a
process that uses the index to then direct the signal to the correct
process. This is course requires a lookup table from index to process Pid,
which can be setup using the scheme outlined before.

Of course, I may not have properly understood the requirement.

Rick Reed -
Tel:+44 1455 55 96 55 Fax:+44 1455 55 96 58 Mob.:+44 7970 50 96 50

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