Re: Robert Dewar's great article about the Strengths of Ada over other langauges in multiprocessing!



"(b" == (see below) <yaldnif.w@xxxxxxxxxxxxxxxx> writes:

<snip>

(b> I think the wording is trying to cover all the bases.
(b> One clue is the phrase "_full_ cache consistency".
(b> The caches certainly need to be consistent with respect to the
(b> protected data, even for protected functions and procedures,
(b> but only entries ensure global consistency and so provide
(b> synchronization of data that is not local to the protected object.

Yes, that seems reasonable.

>> Btw., I ran a simple test on a SPRAC multiprocessor with an entryless
>> protected object containing a single integer versus an integer
>> declared with pragma atomic, and as expected the pragma atomic
>> solution was much (40x) faster.

(b> Unfortunately, we can't usefully apply that pragma even
(b> to a pair of integers. (I don't mean the pair's components!)

Agreed, but you may able to cheat and pack a pair of integers into
a 64-bit atomic, and a compare-and-swap is also much cheaper than a
protected object it seems.

(b> --
(b> Bill Findlay
(b> <surname><forename> chez blueyonder.co.uk



--
C++: The power, elegance and simplicity of a hand grenade.
.