[Robin Becker]
This function from texlib in oedipus.sf.net is a real cpu hog and I determined to see if it could be optimized.
def add_active_node(self, active_nodes, node): """Add a node to the active node list. The node is added so that the list of active nodes is always sorted by line number, and so that the set of (position, line, fitness_class) tuples has no repeated values. """
If you can change the data structure to be an actual list of tuples, then the bisect module can be used directly:
This is a way forward and I think is doable. The original Knuth algo used only global integer arrays. The actual insert point depends on the line attribute only which would be the first tuple element. So apparently we always insert non-identical line breaks at the beginning of their line group; I think we can do the insert check and then a bit of checking to find the actual insert point using bisect_right handwave handwave.....
insert_index = bisect.bisect_left(active_nodes, node) if active_nodes[insert_index] == node: return # avoid creating a duplicate entry active_nodes.insert(insert_index, node)
If the data structure cannot be changed to tuples, then try adding a custom compare operation to the node class:
def __cmp__(self, other): return cmp((self.line, self.position, self.fitness_class), (other.line, other.position, other.fitness_class))
insert_index = nan for index, a in enumerate(active_nodes): if a.line>=node_line: insert_index = index break index = insert_index
This loop can be squeezed a bit more using itertools.imap() and operator.attrgetter() for the attribute lookup:
for index, aline in enumerate(imap(attrgetter('line'), active_nodes): if aline > node_line: . . .
Is there a fast way to get enumerate to operate over a slice of an iterable?
enumerate(s) is the same as izip(count(), s). So, to start from position i, write:
for index, value in izip(count(i), s[i:]): . . .
That being said, your best bet is to eliminate the initial linear search which is likely consuming most of the clock cycles.
Also, I noticed that the code does not reference self. Accordingly, it is a good candidate for being a staticmethod or standalone function.
Raymond Hettinger
-- Robin Becker -- http://mail.python.org/mailman/listinfo/python-list
