Another non-local SIMD algorithm that has been implemented is a method similar to an algorithm due to Shiloach and Vishkin. It is based on the rooted tree approach of the FGHK algorithm (breadth-first search).
This ``Get/Send'' algorithm again has 
iterations
(rather than L), and 
time complexity, since non-local
communications take time 
.
This algorithm is faster in practice than multigrid, both of which are much faster than local label propagation. Currently these are only implemented on SIMD machines, where performance is quite poor due to load balance problems. Should be much better on MIMD machines.