Visualization Visualization Monitor MacMPI contains a communications visualization monitor that visually describes live information about the communications pattern of your cluster during your job's run.

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The top lights describe the communications pattern at that moment, and display differently on different nodes. Red indicates a node is receiving data, green indicates sending data, and yellow means it's swapping data. The middle section displays a log-log histogram of messages sent and received as a function of message size. It encourages you to write your code so you send fewer large messages rather than many small messages, an excellent way to optimize your parallel code. The lower dials indicate estimates of the amount of the time spent communicating and the current bandwidth performance. The colored needles show the momentary measurements and the black needles show the average measurement over the run time of the code.

This monitor window is toggled using a variable named "monitor" in the MacMPI library. When the code is finished MacMPI outputs the accumulated history of the messages sent during the run. When monitor is set to 2, a log of all the messages sent and received is produced in the same file.

You can see this feature demonstrated using the pingpong codes in the Pooch SDK and by activating the MPI Monitor Window item under the Parallel menu of the Fresnel Diffraction Explorer when it is running in parallel.

This feature is available exclusively in the Fortran and C versions of MacMPI_X and the C version of MacMPI_S.

For an in-depth description on how this window responds to a parallel code and how to use it to debug and optimize code, see the Visualizing Message Passing with MacMPI tutorial.