Enabling Probes Selectively

Enable probes based on the characteristics of your source code. For example, if you are interested in the performance of a specific function in your code, and the routines that precede and follow that function are collective routines, enable the collective probes.

When examining a trace file from an MPI program in tnfview, look for events in the Timeline view where synchronization is poor, or where processes are idle. Look for places where sends, receives, or waits spend too much time idle. Create intervals of the start and end probes of blocking sends, receives, and waits, then generate a histogram and look for the taller columns.

In many, if not all programs, enabling only probes on point-to-point routines and collectives will provide enough information to initiate performance analysis.