Computational Complexity
Finding the tree and branch lengths minimizing the least squares residual is an NP-complete problem. However, for a given tree, the optimal branch lengths can be determined in time for ordinary least squares, time for weighted least squares, and time for generalised least squares (given the inverse of the covariance matrix).
Read more about this topic: Least Squares Inference In Phylogeny
Famous quotes containing the word complexity:
“The price we pay for the complexity of life is too high. When you think of all the effort you have to put in—telephonic, technological and relational—to alter even the slightest bit of behaviour in this strange world we call social life, you are left pining for the straightforwardness of primitive peoples and their physical work.”
—Jean Baudrillard (b. 1929)