Message queues

The Message Queues window shows the status of the message buffers of MPI.

You can use it to, for example:

• Show the messages that have been sent by a process but not yet received by the target.
• Detect common errors such as deadlock. This is where all processes are waiting for each other.
• Detect when messages are present that are unexpected, which can correspond to two processes disagreeing about the state of progress through a program.

This feature relies on the MPI implementation supporting it via a debugging support library: the majority of MPIs provide this. Not all implementations support this capability to the same extent, so a variation between the information provided by each implementation is to be expected.