Subject: mpi-context; expense of name service

From: L J Clarke <[email-masked]>
Date: Wed, 30 Jun 93 19:49:53 BST

Hi Jim

You mentioned that the publish/subscribe operations - i.e.  name service
for communicators - is expensive.  I dont think it is that expensive
really.  Observe that mpi_publish and mpi_subscribe are defined such
that when two groups wish to perform a transaction thorugh the name
service just one process does the publish and since mpi_publish is
collective just one process needs to access the server (and the
broadcast the result).  Inference is that name server access is
infrequent and you dont have to worry about the possibility that all
processes hit the server at about the same time.  Of course the user
could write a program which kept hitting the server and this would run
slow but this is the fault of the user provided the performance issues
are properly documented. 

Best Wishes
Lyndon

         /--------------------------------------------------------\
    e||) | Lyndon J Clarke    Edinburgh Parallel Computing Centre | e||) 
    c||c | Tel: 031 650 5021  Email: [email-masked]  | c||c 
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