[m-dev.] parallel conjunction

Ralph Becket rbeck at microsoft.com
Thu Sep 28 01:18:40 AEDT 2000


>From Fergus Henderson on 27/09/2000 15:08:06
> 
> Another alternative would be to document `&' as a standard feature
> equivalent to `,' with no additional restrictions on modes or
> determinism -- just a hint to the implementation to try parallelizing
> things here.  The implementation would then have to issue warnings
> rather than errors if its implementation-specific restrictions are not
> met, and to treat such parallel conjunctions which don't meet its
> restrictions as if they were ordinary conjunctions.

This one sounds about right to me.

> The disadvantage of this approach is that it would require changes
> to the current implementation, and that you'd only get warnings
> rather than errors.  The advantage is that it would ensure portability
> of programs using parallel conjunction to implementations (or grades ;-)
> that don't support real parallelism.

How much of a change to the current implementation would be required?
This parallel conjunction hint is rather like promise declarations - the
compiler is free to take advantage of it if it feels it can do so, otherwise
it has no effect.  On this basis, I'd rather go with option no. 3.
[Btw, do we currently issue warnings about promises the compiler can't 
decipher?]

Ralph

--
Ralph Becket      |      MSR Cambridge      |      rbeck at microsoft.com 

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