Optimal fully adaptive wormhole routing for meshes
Loren Schwiebert, D.N. Jayasimha · 1993
A deadlock-free fully adaptive routing algorithm for 2D meshes which is optimal in the number of virtual channels required and in the number of restrictions placed on the use of these virtual channels is presented. The routing algorithm imposes less than half as many routing restrictions as any previous fully adaptive routing algorithm. It is also proved that, ignoring symmetry, this routing algorithm is the only fully adaptive routing algorithm that achieves both of these goals. The algorithm exploits the fact that for some adaptive routing algorithms, deadlock freedom is possible even when cycles are present in the channel dependency graph. The implementation of the routing algorithm requires relatively simple router control logic. The routing algorithm requires only the minimum number of virtual channels even when extended to arbitrary dimension meshes, yielding a dramatic reduction in the number of virtual channels needed to support fully adaptive routing. Compared to all previous algorithms which required an exponential number of virtual channels with the dimension of the mesh, the new algorithm requires only 4n - 2 virtual channels for an n-dimensional mesh.