[MPICH] Can I ask MPI to not copy the data to shared-mem ?

[Jean-Marc Saffroy]

On Tue, 9 Oct 2007, chong tan wrote:

>  having both sender and reciever being the same shared memory may 
> require Barriers to be placed to block writing to the mem before it is 
> completed consumed.  That may actually slow done the run.

MPI_Isend could still benefit from this approach, eg:
  - process A does Isend (or Irecv), which simply marks the message to be 
sent (or received), then continues with useful computation
  - then process B does Irecv (or Isend), which detects the mark and does 
the actual (and single) message copy, then marks the message as sent
  - then processes A and B eventually do a Wait or Test

It will probably depend on how much the application allows communications 
to overlap with computation (but if it uses Isend/Irecv then it probably 
cares already?).


-- 
saffroy at gmail.com