12.8.2 Monitoring Network State Variables

In order to be able to view network stat variables (e.g., unit activations) in one of the log displays (or record them to disk files), these state variables need to be monitored with a MonitorStat.

The NetView provides a convenient interface for creating monitor stats and selecting which objects to monitor and what values to monitor from them (see section 10.7.1 The Action Region).

There are basically two parameters of relevance in the monitor stat. One is the objects that are being monitored. This is a group which has links to the objects (see section 8.2 Groups for information on links). The other is the variable to record from these objects. Note that if the variable is one found on units, but the object(s) are layers, then the stat will automatically get the unit variable from all of the units in the layer. Similarly, if the variable is one on connections, but the object(s) are projections, all of the connections in the projection will be used.

Typically, the net_agg operator COPY is used. This results in a separate column of data for each object being monitored. This data is stored in the copy_vals group on the monitor stat. When these values are graphed or displayed in the grid log (see section 13.3.4 The Graph LogView, section 13.3.5 The Grid LogView), they appear as one big group that shares the same axis on the graph and is part of the same sub-grid on the grid.

However, one can compute any kind of network aggregation from the monitored statistics. For operators other than COPY, the results go in the mon stat value member.

It is also possible to perform three steps of pre-processing on the monitored values before they are recorded or aggregated into the monitor stat. This pre-processing is controlled by the pre_proc_1,2,3 members, which specify an operation and, optionally, arguements to that operation in the arg member. Note that the thresholding function THRESH compares the value to the arg, and gives a result of hi if it is greater-than-or-equal, and lo if it is less-than the arg.