[ptp-user] Now, here's a bug!

["Dr. David E Hudak" <dhudak@xxxxxxx>]

Hi PTP community,

I found a bug in the eclipse-supplied MPI C example that calculates Pi.

The broadcast on line 93:
	MPI_Bcast(message, strlen(message)+1, MPI_CHAR, dest, MPI_COMM_WORLD);
..fails because rank 0's message buffer is "Hi, how are you?" and ranks 1..num_procs-1 message buffer is "Greetings from process 1", "Greetings from process 2", and so on.  This leads to calling the MPI_Bcast with different buffer lengths which causes a fault on my cluster.  

I recommend it be changed to match the fortran example where everyone uses the max length of the buffer for the broadcast, like so:
	MPI_Bcast(message, 100, MPI_CHAR, dest, MPI_COMM_WORLD);

I tested this change on my cluster and it works.  

I would like a refund for the 30 minutes of my life this bug has taken from me.  Put it on my tab :-)

Thanks,
Dave
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David E. Hudak, Ph.D.          dhudak@xxxxxxx
Senior Research Scientist
Ohio Supercomputer Center
http://www.osc.edu/~dhudak