20.181/Lecture6

Exams and HWs

 * In-class midterm on 10/11
 * studying for the exam:
 * don't memorize lecture notes,
 * more important to be able to work through the problems
 * understand all the homeworks and you'll be prepared

Homeworks coming up

 * HW5: Due next wednesday
 * downPass, maximum likelihood


 * HW6:
 * search tree space

Up Pass

 * If we know what the best answer is at the root- all of the other internal nodes aren't necessarily the best guess. We need an upPass algorithm that passes information from the root, back up to the leaves.


 * For this example, we are dealing with one column of the sequence alignment. In this simple example, we compute one possible set of internal states (but we learned that this doesn't cover all possible states - see lecture 7 for details):

 def upPass(tree,parent):
 * if tree is a leaf: #(stop)
 * return
 * i = parent downpass
 * if i = None:
 * data = i downpass
 * upPass(left,data)
 * upPass(right,data)

