On 9 Sep 2010, at 21:10, jody wrote:

> Hi
> @Ashley:
> What is the exact semantics of an asynchronous barrier,

I'm not sure of the exact semantics but once you've got your head around the 
concept it's fairly simple to understand how to use it, you call MPI_IBarrier() 
and it gives you a handle you can test with MPI_Test() or block for with 
MPI_Wait().  The tricky part comes in how many times you can call 
MPI_IBarrier() on a communicator without waiting for the previous barriers to 
complete but I haven't been following the discussion on this one to know the 
specifics.

> and is it part of the MPI specs?

It will be a part of the next revision of the standard I believe.  It's been a 
long time coming and there is at least one implementation out there already but 
I can't comment on it's usability today.  To be clear it's something I've long 
advocated and have implemented and played around with in the past however it's 
not yet available to users today but I believe it will be shortly and as you'll 
have read my believe is it's going to be a very useful addition to the MPI 
offering.

Ashley,

-- 

Ashley Pittman, Bath, UK.

Padb - A parallel job inspection tool for cluster computing
http://padb.pittman.org.uk


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