The.Algorithm.Design.Manual.Springer-Verlag.1998

War Story: Nothing but Nets
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War Story: Nothing but Nets
I'd been tipped off about a small printed-circuit board testing company nearby that was in need of some
algorithmic consulting. And so I found myself inside a typically non-descript building in a typically nondescript
industrial park, talking with the president of Integri-Test, along with one of his lead technical
people.
``We're the leaders in robotic printed-circuit board testing devices. Our customers have very high
reliability requirements for their PC-boards. They must check that each and every board has no wire
breaks before filling it with components. This means testing that each and every pair of points on the
board that are supposed to be connected are connected.''
``How do you do the testing?'' I asked.
``We have a robot with two arms, each with electric probes. To test whether two points are properly
connected, the arms simultaneously contact both of the points. If the two points are propertly connected,
then the probes will complete a circuit. For each net, we hold one arm fixed at one point and move the
other to cover the rest of the points.''
``Wait!'' I cried. ``What is a net?''
Figure: An sample net showing (a) the metal connection layer, (b) the contact points, (c) their minimum
spanning tree, and (d) the points partitioned into clusters
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