[mpich-discuss] Optimal implementation of an interesting social network model --open for discussion
Pavan Balaji
balaji at mcs.anl.gov
Thu Oct 27 22:11:48 CDT 2011
This mailing list is only for MPICH2 specific questions.
-- Pavan
On 10/26/2011 05:03 PM, Jierui XIE wrote:
> Dear All,
>
> Here is the simplified model for a social network application with N
> nodes (millions of nodes). Each node has a memory M (the capacity is
> T ). This model is also a iterative algorithm. The number of
> iterations is T.
>
> At each time step t, each node i does the following two things:
> Job 1: First,it generates a label x based on its memory, i.e., x=gen1(M).
> It then sends c to all its neighbors nbs(i).
> Job 2: Second, it receives labels from all its neighbors (one label
> for one neighbor).
> It then computes another label y based on received labels,
> i.e., y=gen2(M) and then
> adds y to its memory M.
>
> After all nodes perform the above two jobs, let t=t+1.
> The entire algorithm stops when T is reached.
> ----------------------------------------------------------------
> One challenge I see is, it is not easy to have an optimal partition of
> nodes, such that the communication cost is lower.
> For example, suppose that we partition N nodes to total G groups (each
> goes to one process), each group receives and sends labels to ONLY
> their neighbors. It seems that in this way, the number of 'labels'
> exchanged is minimum. However, each group may has many neighbors in
> many other groups (processes), the communications are very likely to
> involve many processes (groups).
>
> One plausible solution is to ask a master node to collect all the
> labels from Job 1 of ALL nodes, then broadcast ALL these labels to ALL
> the processes to perform Job 2. However, since the network is very
> large, the storage capacity (for all labels) on each node and also the
> cost of broadcasting may become new issues.
>
> Hope I make it clear.
> ----------------------------------------------------------------
> Do you see any other problems in implementing this algorithm or any
> other better solutions?
>
>
>
> Jerry
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--
Pavan Balaji
http://www.mcs.anl.gov/~balaji
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