Using the XPVM GUI

The xpvm graphical user interface to PVM is a nice visualization tool for developing, testing and debugging PVM programs. The xpvm program has built in help and is intuitive and simple to use. Similar to the PVM console program, pvm, the xpvm program starts up the PVM system with the list of nodes allocated by the PBS system. Then the user can use it to run parallel programs, visualize the execution, look at the output from all nodes, debug multiple nodes simultaneously, check utilization of the cluster during execution of the parallel program, check message queue length during execution and other features. A powerful feature of xpvm is its ability to graphically playback the sequence of events during an execution. This allows the user to investigate the behavior of a parallel program without having to spend a lot of time rerunning the parallel program. The following figure shows a screenshot of xpvm in action.

As with the PVM console program, remember to halt the PVM system from the xpvm GUI when you are done and then exit from the PBS session to release all resources.

To start xpvm, acquire nodes using pbsget and then start xpvm.

[amit@onyx amit]$ pbsget -4
 ...
qsub: waiting for job 820.onyx.boisestate.edu to start
qsub: job 820.onyx.boisestate.edu ready

[amit@onyx PBS ~]:xpvm
xpvm: Using list of machines from PBS.
New PVMD started... XPVM 1.2.5 connected as TID=0x40001.
[globs.tcl][procs.tcl][util.tcl]
Initializing XPVM.............................................. done.
%

The xpvm will start up in a new window. Initially it will ask you want to overwrite the trace file. You can answer ``Yes'' here. The main xpvm window will have two panels: Network View and Space Time View.

Running a PVM program. Go to Tasks...menu, then click on Spawn option to get the spawn window. In the Command: field you can type in the name of your program along with the command line arguments. Next select the PvmHostCompl button. Then select the Host button. A new field labeled Host will show up. Type the internal name of the master node, node00, here. The purpose of the last two steps to ensure that the PVM processes are not scheduled on the master node. Next type in the number of SPMD tasks you want to spawn in the NTasks field. Finally click on the Start button to start the parallel program.

Checking output from your program. As the parallel program runs, the Network View and the Space Time View are updated. You can also see the combined output from all the nodes by selecting the Views... menu and selecting the Task Output choice. A separate task output window will appear.

Other useful features. You can also go to the Views...menu and select the Utilization choice. This will show the node utilization in a separate window. Similarly you can look at message queue length with Views... and then Message Queue. The following screenshot shows some of the above examples.

As with the PVM console program, remember to halt the PVM system from the xpvm GUI when you are done and then exit from the PBS session to release all resources. To halt PVM, go to the File menu and then select Halt PVM choice.