TotalView Users Guide - CI Wiki

Figure 90: Message Queue
Window Showing Pending
Receive Operation
Displaying the Message Queue
Diving on MPI Buffers
When you dive into the buffer fields, TotalView opens a Variable Window. It
also guesses what the correct format for the data should be based on the
buffer length and the data alignment. You can edit the Type field within the
Variable Window, if necessary.
TotalView doesn’t use the MPI data type to set the buffer type.
About Pending Receive Operations
TotalView displays each pending receive operation in the Pending receives
list. Figure 90 shows an example of an MPICH pending receive operation.
TotalView displays all receive operations maintained by the IBM MPI library. Set the
environment variable MP_EUIDEVELOP to the value DEBUG if you want blocking
operations to be visible; otherwise, the library only maintains nonblocking operations.
For more details on the MP_EUIDEVELOP environment variable, see the IBM Parallel
Environment Operations and Use manual.
About Unexpected Messages
The Unexpected messages portion of the Message Queue Window shows
information for retrieved and enqueued messages that are not yet matched
with a receive operation.
Some MPI libraries, such as MPICH, only retrieve messages that have
already been received as a side effect of calls to functions such as
MPI_Recv() or MPI_Iprobe(). (In other words, while some versions of MPI
may know about the message, the message may not yet be in a queue.)
This means that TotalView can’t list a message until after the destination
process makes a call that retrieves it.
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