def add_node(dyad, parent_node):
"""Make a cost-scored node from a target pair dyad. Use memoized cost lookups for speed"""
matches = [x for x in parent_node.children if x.name == dyad]
if not any(matches):
n = Node(dyad)
n.cost = get_cost(dyad)
n.parent = parent_node
else:
n = matches[0]
return n
def make_tree():
"""Iteratively build a tree of unique, valid tetrads. A valid tetrad has 4 target dyads
whose elements obey the relationship {(a, c), (a, d), (b, c), (b, d)} """
# memoized cache of previously-added valid tetrads to prevent duplication.
valid_tetrads = set()
root = Node('root')
root.cost = 0
# bush_root is A and C
for parent in dyad_pairs:
# all children are A and D
br_children = [
d for d in dyads if parent[0] == d[0] # is a
and parent[1] != d[1]
] # is not A.
for child in br_children:
# all grandchildren are B and C
grandchildren = [
d for d in dyads if d[0] != parent[0] # not a
and d[0] != child[1] # not d
and d[1] == parent[1]
] # is c
for grandchild in grandchildren:
# all greatgrandchildren are B and D
greatgrandchildren = [
d for d in dyads
if d[0] == grandchild[0] and d[1] == child[1]
]
for greatgrandchild in greatgrandchildren:
tetrad = make_tetrad(parent, child, grandchild,
greatgrandchild)
if is_valid(tetrad) and tetrad not in valid_tetrads:
valid_tetrads.add(tetrad)
parent_node = add_node(parent, root)
child_node = add_node(child, parent_node)
grandchild_node = add_node(grandchild, child_node)
greatgrandchild_node = add_node(
greatgrandchild, grandchild_node)
print(f'processed bush with root {parent}')
print(
f'took {(datetime.now() -start).total_seconds()} to generate full tree before pruning'
)
return root
