Newsgroups: comp.parallel.mpi
From: Bogdan Udrea <udrea@aa.washington.edu>
Subject: Q: MPI packing vs. MPI derived data types
Organization: University of Washington
Date: Tue, 24 Mar 1998 09:10:46 -0800
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Message-ID: <Pine.OSF.3.95.980324085818.4331A-100000@endeavor.aa.washington.edu>

Hello MPI folk.

I have a few questions related to the efficiency of point-to-point
communications using MPICH 1.x

Some time ago I performed timing runs for passing data using MPI
packing and MPI derived data types. Both methods were used to pass 
2D "faces" out of 3D arrays. I used MPICH 1.x on DEC Alpha's and
found out that derived data types (DDT) are faster than packages. 
On the average the DDTs were seven times faster than the packages.
Maxima were at about 10 times and minima at about 3 times (I assume
due to network loading.) 

My questions are:

1. Has anybody else performed this type of comparison? 

If yes,

2. Are the results in the same range?
3. Is it safe to assume that this holds for other implementations of MPI
   besides MPICH?

Thanks a lot.

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