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*To*: occam-com@xxxxxxxxx*Subject*: Dynamic Priority*From*: Adrian Lawrence <adrian.lawrence@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx>*Date*: Mon, 26 Apr 1999 20:25:36 +0100 (BST)

Dynamic Priority ~~~~~~~~~~~~~~~~ Starting from existing occam, we may as well leave PAR as it is. Although HARD PAR or SOFT PAR or TRANSPARENT PAR or PAR(HARD) may be needed. But we can have an optional CHAN parameter in PRI PAR: I think that this is the more accurate representation. PRI PAR(CHAN OF something priority) P0 P1 ... PN Specifying the POR (Partial Order Relation) ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ The syntax gives a reference order. My original idea of sending the ordered image of a bijection as a table of indices is simple, and I hope lightweight for the sender to prepare, and for the implementation to utilize. It is pretty much a preprepared lookup table of offsets. Gerald raises the idea of a more general order relation. Do we need this? Will it ever be needed? Anyway, one more general possibility is to have a list of ordered sets: S0 > S! > S2.... For example {P0} > {P2,P3} > {P1,P4,P5} would correspond to PRI PAR P0 PAR P2 P3 PAR P1 P4 P5 . Since each set Si could be represented by a bit list, this could be sent as bit arrays (packed into INTs I guess, with a restriction of bits_in_word, in a given set). Of course, if we ever have real BIT arrays as I suggested a few years ago, this is another application. :-) So above would be specified as 00000001,00001100,00110010 in 8-bit words. No doubt there are many ways to do this, and perhaps we could define specific protocols to encode them. But do we need any of this? Adrian -- A E Lawrence, MA., DPhil. adrian.lawrence@xxxxxxxxxxxxxx MicroProcessor Unit, 13, Banbury Road, Oxford. OX2 6NN. UK. Voice: (+44)-1865-273274, Fax: (+44)-1865-273275

**Follow-Ups**:**RE: Dynamic Priority***From:*Gerald Hilderink

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