[mpich-discuss] single vs multiple communicator

[Pavan Balaji]

The second option will be slower.  Apart from the fact that the MPI implementation needs to manage a large number of communicators, in most implementations this option will disable shared memory communication between the slave and master.

  -- Pavan

> On May 11, 2015, at 7:17 AM, Roy, Hirak <Hirak_Roy at mentor.com> wrote:
> 
> Hi MPICH team,
>  
> I have an application which is mostly using master-slave kind of architecture. One master and <n> number of slaves. The slaves do not communicate between themselves and only sends/receives messages to/from master.
>  
> I have two ways I can setup the application
> 1>    Static : Master and slaves are all in the same MPI World
> 2>    Dynamic : Each slave is connected to master using a MPI_Comm and the communicator is created using MPI_Comm_connect/MPI_Comm_accept. Essentially master has <n> communicators.
>  
> The way master works is : it uses MPI_WaitAny kind of method to check messages from slave.
>  
> Could you please tell me whether <2> can be significantly slow with respect to  <1> if all the slaves send lots of small messages?
> Is there some kind of buffering overhead in <2> for <n> communicators and which can be solved using some configuration.
>  
> Thanks,
> Hirak
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