[ndnSIM] Mpi on multiple machines

[Alex Afanasyev]

> On Jul 7, 2016, at 6:52 AM, Andriana Ioannou <ioannoa at tcd.ie> wrote:
> 
> Hey Alex,
> 
> Many thanks for the reply.
> 
> I have managed to make it work on a single machine with multiple processors - not multiple machines - as this was useless to me anyway.  What I wanted to do was to distribute the memory consumption between the different machines. However, my memory consumption comes from the structure of a node which can not be discarded even when using an mph - the whole topology is to be created on each LP anyway.
> 
> Now, with regard to the mpi usage, I have noticed the below:
> 
> 1. The simulation runs differently on a single processor compared to the one using an mpi. That said, the requests are triggered with a different sequence.

If events are scheduled for the same nanosecond of simulation time, the order of events would be undetermined.  However, if the time is different, they should be in pre-determined order, no matter single processor or MPI.  If there are differences, then there is some issue somewhere.

> 
> 2. Different apps may create Interests with the same nonce, which is “misleading" to the performance of the system as they may be treated as duplicas - while they are not.

Hm.. Given nonce is random, there is possibility that nonce collide. But this should have extremely low probability to happen.  Do you see it consistently?  (Is it for ndnSIM 2.x?)

--
Alex

> 
> Any ideas on how to deal with the above?
> 
> Thanks,
> A.
> 
>> On 27 Jun 2016, at 05:28, Alex Afanasyev <aa at cs.ucla.edu> wrote:
>> 
>> I have tried it once long time ago and the process was relatively straightforward (though, I completely forgot all the details).  You just need to select where mpi processes should run and afterwards everything happens automatically.  (Just in case, the key catch with MPI is that you need to properly partition the topology to get benefits of MPI, and partitioning is not always trivial...)
>> 
>> --
>> Alex
>> 
>>> On Mar 19, 2016, at 8:41 AM, Andriana Ioannou <ioannoa at tcd.ie> wrote:
>>> 
>>> Hello all,
>>> 
>>> I was wondering whether someone has any feedback/advice on the use of mpi onb multiple machines. From reading the post, I do assume that is possible but I am rather confused on how to proceed with it exactly.
>>> 
>>> Any help would be great.
>>> 
>>> Thanks.
>>> A.
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>> 
> 

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