Sascha Roloff <sascha.rol...@googlemail.com> wrote on 05/25/2011 06:56:08
AM:
>
> I have a program using more than one places. Now I am starting several
> concurrent activities on different places which execute an algorithm
that
> needs mutual exclusion against the other activities on all other places,
so
> it also has to communicate with the other places. Is it possible in any
way
> to realize a mutual exclusion involving more places.
Hmm, this doesn't sound like a parallel algorithm. Do you really have to
execute one activity at a time?
As to the atomic operations, X10 language spec says it guarantees mutually
exclusive operations at the same place. Nothing I'm aware of working for
more than one places.
I tried already
things
> with locks and monitors from the X10 standard library and experimented
with
> such kind of code:
>
> val lockRef = GlobalRef[Lock](new Lock());
>
> for(p in Place.places()) {
> at (p) async {
> // enter atomic
> at (lockRef.home) {
> val lock = lockRef();
> lock.lock();
> }
> ...
> // leave atomic
> at (lockRef.home) {
> val lock = lockRef();
> lock.unlock();
> }
> }
> }
>
> I know, this is not very desirable and not very performant.
This looks like a sequential code, but much more convoluted unfortunately.
Use a single global entity for lock/unlock is not scalable. Other PGAS
languages normally do is to use disjoint data (e.g. use DistArray) for
locking operations. It will yield better scalability.
But again, if your algorithm is not parallel, then choosing a "good"
locking mechanism is a waste of time.
Cheers,
Jim Xia
Compiler Testing, X10 & XLF
IBM Toronto Lab at 8200 Warden Ave,
Markham, On, L6G 1C7
905-413-3444
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