Although timing can provide insight into the performance of a program, it is sometimes desirable to see in detail the sequence of communication and computational events that occurred in a program and the amount of time spent in each phase. This information is usually gained by tracing various events during execution, ie., logging information as the parallel program runs. Files that contain time-stamped communication and computational events are called logfiles. The easiest way to understand this data at a glance is with a graphical tool. In the next two subsections, creation of a logfile using MPE logging routines and viewing of the logfile using the program upshot are described.