QLogic OFED+ Host Software User Guide, Rev. B

F–Troubleshooting
QLogic MPI Troubleshooting
Statistics other than MPI-level statistics are fairly low level; most users will not
understand them. Contact QLogic Technical Support for more information.
Message statistics are available for transmitted and received messages. In all
cases, the MPI rank number responsible for a minimum or maximum value is
reported with the relevant value. For application runs of at least three ranks, a
median is also available.
Since transmitted messages employ either an Eager or a Rendezvous protocol,
results are available relative to both message count and aggregated bytes.
Message count represents the amount of messages transmitted by each protocol
on a per-rank basis. Aggregated amounts of message bytes indicate the total
amount of data that was moved on each rank by a particular protocol.
On the receive side, messages are split into expected or unexpected messages.
Unexpected messages cause the MPI implementation to buffer the transmitted
data until the receiver can produce a matching MPI receive buffer. Expected
messages refer to the inverse case, which is the common case in most MPI
applications. An additional metric, Unexpected count %, representing the
proportion of unexpected messages in relation to the total number of messages
received, is also shown because of the notable effect unexpected messages have
on performance.
For more detailed information, use MPI profilers such as mpiP. For more
information on mpiP, see: http://mpip.sourceforge.net/
For information about the HPCC benchmark, see: http://icl.cs.utk.edu/hpcc/
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