[mpich-discuss] Order of completion in MPI_Waitany

[Matthieu Dorier]

Hi, 


I would like a precision on the semantics of MPI_Waitany in this situation: 


- Process 1 does 2 MPI_Irecv with different tags A and B (the order doesn't matter); it then waits on the two requests with MPI_Waitany. 
- In the mean time, process 2 does an MPI_Send with tag A, then MPI_Send with tag B. 
Can I ensure that MPI_Waitany will always give me the index of the message corresponding to the first MPI_Send, i.e. the one with the tag A, even in situations where process 1 called MPI_Irecv on a tag B first? 


Thanks 


Matthieu Dorier 
PhD student at ENS Cachan Brittany and IRISA 
http://people.irisa.fr/Matthieu.Dorier 
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