Steiner tree (RSMT)
Beginner
The shortest way to connect several points with wires when you may add new junction points along the way.
Novice
A branching set of wires that connects all pins of a net and may add extra junctions, called Steiner points, where no pin exists. The rectilinear Steiner minimum tree (RSMT) is the shortest such tree built only from horizontal and vertical segments.
Expert
Finding an RSMT is NP-hard, but Hanan’s theorem limits Steiner points to the grid formed by the pins’ and lines, and lookup-table methods such as FLUTE are exact and fast for nets with fewer than 10 pins. Global routers use them to break nets into two-pin connections.