Parallel program visualization.

Distributed with p4 is a portable library called alog for producing log files of user-specified events. These files can then be examined with a variety of tools. One that we have used extensively for some time for studying the behavior of p4 programs is upshot [14,19]. In Figure we see upshot being used to display details of a run made on the parallel automated reasoning system described above. alog is also used to instrument p4 internally. If certain compile-time switches are set, any p4 program will produce alog logfiles. alog is not directly tied to p4; it has also been used to instrument a variety of other parallel programming systems.