Displaying Communicator Data

Prism displays MPI Communicators in the Communicators region of the MPI queue visualizer window. The visualizer does not display all the communicators that have been created in an MPI program; rather, it displays only communicators referenced by currently posted messages. Thus, if no messages are visible, then the visualizer displays no communicators.

Prism displays as many as three distinct communicators. Each communicator is color coded, and messages are drawn using the color of their communicator. If more than three communicators are present, then the excess are grouped together under a single color labeled Others.

You can change colors for the communicators by setting the following X resources in the Prism application defaults file:

• Prism.comm1Color

• Prism.comm2Color

• Prism.comm3Color

• Prism.commOtherColor

For information about modifying values in the Prism applications defaults file, see " Changing Prism Defaults".

Figure 5-26 shows the Communicator dialog box. Press any of the communicator buttons to reveal the Communicator dialog box, displaying the following information:

• Name

• Address - The address of the communicator.

• Fortran handle - The Fortran identifier for the communicator, if defined. Built in communicators such as MPI_COMM_WORLD have predefined Fortran handles. Other communicators are assigned a Fortran handle only if they are used in a Fortran subroutine.

• Topology - The options are:

  • Cartesian - Communicators created using MPI_Cart_create.

  • Graph - Communicators created using MPI_Graph_create.

  • None - All others.

• Size - The number of ranks.

• Remote Size - Shown only for intercommunicators; the size of the remote group (the number of ranks). For information about intercommunicators, see the MPI_Intercomm_create man page.

• Ranks - The list of ranks, possibly annotated with job identifiers if the communicator was created via an MPI client/server rendezvous or an MPI_Spawn. The ranks displayed for a communicator are relative to MPI_COMM_WORLD, rather than relative to the communicator's parent.

Figure 5-26 Communicator Dialog Box