[mpich-discuss] MPI_Send and MPI_Bcast

msi msi at anl.gov
Wed Sep 7 08:18:38 CDT 2016


    
Hi Alaa,
Generally, for small number of processes, the performance of MPI_Bcast is usually equal to MPI_Isend/MPI_Recv, for large number of processes, broadcast should be better.
Could you please try the lateat version of MPICH on you system ? MPICH2 is very old. 
Please also give us following information.Number of processesNumber of processes per nodeThe execution time of each algorithm
Min


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-------- Original message --------
From: alaa nashar <nashar_al at yahoo.com> 
Date: 9/7/2016  7:04 AM  (GMT-06:00) 
To: discuss at mpich.org 
Subject: [mpich-discuss] MPI_Send and MPI_Bcast 

 Dear
all

 

I have
implemented the following two algorithms on my home Ethernet LAN containing 2/
and three heterogeneous devices using MPICH2.

 

Algorithm1:

1- Root
process reads the contents of an input array.

2- It
then sends the array data to all other processes.

3- All
processes including the root process perform specific

  
computations on their array copies.

4- Once
the computations within each process are finished,

  
the generated arrays are directly written by the process that

  
performed the computations to separate files.

 

Algorithm2:

Same as
Algorithm 1 except step 2 is replace by:

2- Root process broadcast the array data to all other processes.

 

The
implementation of both algorithms  work fine and give the expected results
but Algorithm2 that uses MIPI_Bcast is slower than Algorithm1 that uses
MPI_Send

 

For my
knowledge, MIPI_Bcast is faster than MPI_Send.

Please,
would you guide me to know if there is any conflict of misunderstand.

 

Thanks
a lot

 

Alaa

 
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