MGR: Multi-level global router

Global routing faces an increasing problem size and urgent demand on improvement in solution quality. Despite of the recent developments of global routers, there exist only two types of choices: slow 3D routers with good solution quality or efficient 2D routers with relatively poor solution quality. We propose a multi-level 3D global router called MGR to fill the gap. MGR resorts to an efficient multi-level framework to reroute nets in the congested region on the 3D grid graph. Routing on the coarsened grid graph speeds up the global router while 3D routing introduces less vias. The powerful multi-level rerouting framework wraps three innovative routing techniques together: adaptive resource reservation in coarsening process, a new 3-terminal maze routing algorithm and network flow based solution propagation in uncoarsening process. As a result, MGR can achieve the solution quality close to 3D routers with comparable runtime of 2D routers.