Newsgroups: comp.parallel.mpi
From: csv@parcom.ernet.in (Chaman Singh Verma)
Subject: HELP ME IN UNDERSTANDING
Organization: Centre for Development of Advanced Computing (C-DAC), Pune, INDIA.
Date: Tue, 18 Jul 1995 13:31:50 GMT
Message-ID: <DBwyx8.6xI@parcom.ernet.in>

Hello,

This one is to clarify some doubtes in the MPI implementation. 
The problem is that when we are trying to exclude some process 
from one particular group, then why do we need to write these 
three lines in the processor which is being excluded.

Call MPI_Comm_Group(MPI_Comm_world, World_Group, Ierror)
Call MPI_Group_Excl(World_Group, 1, 0, Worker_Group, Ierror)
Call MPI_Comm_create(MPI_Comm_World, Worker_group, MPI_Comm_Worker, 
                     Ierror)

MPI book says that first two calls are local, and the third one 
should be called from each processor, even if it is not in the 
new group. Why ? I am unable to understand the logic behind this 
because the processor which is being excluded is not used for the 
communication. 

Perhaps I am unable to understand these trivial issues of MPI Implementation.

Thanx 

Chaman Singh Verma

C-DAC PUNE INDIA 
csv@parcom.ernet.in

   


