When NETEX first processes a GDSII file it extracts all of the nets (with one exception: see the -tstpt option) and writes an intermediate output file even if the user has requested only a single net.

left: the entire net output. right a single net output takes 95% of the work to generate.

Why?

It turns out that to extract a single net, NETEX must booleanize the entire database, perform the intersection routines on the entire file -- in effect it takes 95% of the computation to extract a single net and only an additional 5% to extract 100% of the nets.

By saving the results, NETEX can do additional extractions with very little effort.

When NETEX processes a file, it examines the configuration file (.cfg) and looks for an entry called LASTRUN. If LASTRUN is found, then it checks to see that the file name, the technology file, the structure and the window are identical to this run. If so, it knows that it can use the intermediate file and does not need to repeat the computations to explode, flatten, booleanize etc... but can go straight to the net extraction routines.

The LASTRUN section will be written by NETEX and should not be edited or modified by the user. A sample is shown below.

LASTRUN
INPUT nettest.gds
TOP top_test
WINDOW ALL
TECH test.tech
ENDLASTRUN