Hello,
Passive Synchronization is the one you might want to use because although
the target process does not take part in either Synchronization or
Communication it does receive the data sent by the sender. I amn't sure
what you mean by 'pick up computation'.
You could try something like:
1. Create Windows on target processes 2 and 3
2. if (x < 0.5)
/* Lock the window on Process 2, put data and unlock window */
MPI_Win_lock()
MPI_Put()
MPI_Win_unlock()
else
/* Similarly for Process 3 */
endif
3. Free the windows on process 2 and 3.
Hope this helps.
Prashanth Charapalli,
LAM/MPI Team.
Thus spake Lei_at_ICS in the message sent on Tue, 9 Mar 2004
->Hi Prashanth,
->
->Thanks a lot for your help.
->
->Let us take a look at all possible synchronization
->mechanisms.
->
->1). Passive: The target process takes no part in either
-> the synchronization nor the communication. This is
-> not what I wanted since I would like the target
-> to pick up the computation for efficient data accessing
-> of the array A[].
->
->2). Active: There are two sub-classes:
-> a). Collective synchronization: Obviously this one uses
-> MPI_WIN_FENCE() which is a global synchronization.
-> b). Pair-wise synchronization: This is probably the closest.
-> But the target would need to know that it needs to
-> call MPI_WIN_POST() and MPI_WIN_WAIT(). Notice that
-> in my example, I assume the decision factor X is
-> only available on p1. So the actual target, p2 or p3
-> depending on the value of X, would not know that
-> it is supposed to call MPI_WIN_POST() and MPI_WIN_WAIT(),
-> unless a broadcast of X is made.
->
->Maybe I am missing something in the above. Could you show
->me with simple pseudocode how this can be done please?
->
->Thanks a lot,
->-Lei mailto:pan_at_[hidden]
->
->Tuesday, March 9, 2004, 6:51:05 PM, you wrote:
->
->
->P> Hello,
->
->P> MPI_Put probably provides the functionality you are looking for. MPI_Put
->P> though requires that the receiving process have a buffer large enough to
->P> hold the data that is being 'put'.
->
->P> The following URL seems to give very good information on MPI_Put and the
->P> subsequent synchronization needed (not necessarily global).
->
->P> http://www.epcc.ed.ac.uk/overview/publications/training_material/tech_watch/98_tw/techwatch-mpi2/MPI2-3.html
->
->P> MPI_Put does not require global synchronization nor global broadcasting.
->
->P> Hope this helps.
->
->P> Prashanth Charapalli,
->P> LAM/MPI Team.
->
->
->P> Thus spake Lei_at_ICS in the message sent on Tue, 9 Mar 2004
->
->->>Hi all,
->->>
->->>The following simple example illustrates
->->>what I wanted to do with one-sided communication.
->->>
->->>I have three processors p1, p2, and p3.
->->>On p1 there is a large array A[10000]
->->>that needs to be sent to p2 or p3 depending
->->>on a parameter X which is computed on
->->>p1. X is not available initially on p2 or p3.
->->>
->->>if(X < 0.5)
->->> put A[10000] to p2;
->->>else
->->> put A[10000] to p3;
->->>
->->>Now after this I want whoever owns A[]
->->>to compute using it. In other words,
->->>p2 or p3, but not p1 will compute using A[].
->->>This is for efficiency.
->->>
->->>I would like to have p2 or p3 be interrupted
->->>or awakened by p1 only when the data A[]
->->>is coming to the processor. In other words,
->->>the one who does not get the data should
->->>not waste a single CPU cycle doing busy
->->>waiting. A solution with a global synchronization
->->>or broadcasting is not desirable.
->->>
->->>Is there a way to do it with MPI-2 one-sided
->->>communication?
->->>
->->>Thanks a lot for your help in advance,
->->>-Lei mailto:pan_at_[hidden]
->->>
->->>_______________________________________________
->->>This list is archived at http://www.lam-mpi.org/MailArchives/lam/
->->>
->
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