Fig. 2From: Optimization of sequence alignments according to the number of sequences vs. number of sites trade-offTree traversals. Recursion orders for initializing down and up arrays. Notations are as introduced in Fig. 1. i and i+1 show operations performed during two subsequent iterations. a first, post-order tree traversal, initializing all down arrays from the leaves to the root. b second, pre-order tree traversal, initializing the up arrays from the root to the leavesBack to article page