. The boot schema from which LAM is started can be provided to XMPI so that it may be presented as an inventory of nodes on which programs may be run.

       Application Overview

        The state information is obtained from one or two sources, a running application started by XMPI or a file containing trace data from a traced MPI application. When XMPI is started, its top-level overview window is blank. Once an application is started or a trace file is loaded, the overview window fills with a tiled group of hexagons, each representing the state of one MPI process.

Application Overview: processes and messages at a glance

A traffic light symbol indicates wether the process is running or blocked. No traffic light is shown for processes which have either finalized or not yet initialized the MPI library.

Process Focus

        A process window with full MPI details on a single process and its unreceived messages is popped up by a mouse click on an interesting cell in the application overview. Several process windows may be on the screen simultaneously so that the user can focus on problem interactions between a few processes. When monitoring a running application the camera "Snap" button or "Snapshot" item in the "Application" menu updates the state information on all processes at any time.

Process Focus: details on process status and its unreceived messages

The datatype button displays the type map.
The next button shows the next group of identical messages.
The group button highlights the members of the communicator's process group.

         If the process is blocked, the function name, peer process rank, communicator, message tag and element count are displayed. If unreceived messages are available, their quantity, source process rank, communicator, message tag and element count are displayed. By leaving a few process windows on the screen, a user can focus debugging on a small and manageable colection of misbehaving processes.

Communication Trace Visualization

XMPI can cause the communication activity of an application to be traced. The resulting trace data can be extracted at runtime or after the application completes. The trace data is visualized in two tried and true ways: the communication timeline and the kiviat radial chart (see chapter III). Using a dial in the timeline window, a snapshot of the application state can be taken as if the same snapshot was taken at the selected time during the application's run. The results are displayed in the same manner, using the overview window and the processes windows.

Communication Timeline: Placing the dial gives a full snapshot of MPI details.

        The "Clean" button or "Clean" item in the "Application" menu terminates an application and the development cycle can be repeated. The previous application can be rerun with the "Rerun" button or "Rerun" item in the "Application" menu.