srenblad/artiq
1
0
Fork 0
forked from M-Labs/artiq
Code Pull Requests Activity

compiler: proper union find

Browse Source 
The find implementation was not very optimized, and the unify function
did not consider tree height and may build some tall trees.
This commit is contained in:
pca006132 2021-07-07 09:20:41 +08:00 committed by Sébastien Bourdeauducq
parent 4ede58e44b
commit b10d1bdd37
1 changed files with 20 additions and 21 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

41
artiq/compiler/types.py
View File

@ -55,40 +55,39 @@ class TVar(Type):
def __init__(self):
self.parent = self
self.rank = 0
def find(self):
if self.parent is self:
parent = self.parent
if parent is self:
return self
else:
# The recursive find() invocation is turned into a loop
# because paths resulting from unification of large arrays
# can easily cause a stack overflow.
root = self
while root.__class__ == TVar:
if root is root.parent:
break
else:
root = root.parent
# path compression
iter = self
while iter.__class__ == TVar:
if iter is root:
break
else:
iter, iter.parent = iter.parent, root
return root
while parent.__class__ == TVar and root is not parent:
_, parent = root, root.parent = parent, parent.parent
return root.parent
def unify(self, other):
if other is self:
return
other = other.find()
if self.parent is self:
self.parent = other
x = other.find()
y = self.find()
if x is y:
return
if y.__class__ == TVar:
if x.__class__ == TVar:
if x.rank < y.rank:
x, y = y, x
y.parent = x
if x.rank == y.rank:
x.rank += 1
else:
y.parent = x
else:
self.find().unify(other)
y.unify(x)
def fold(self, accum, fn):
if self.parent is self: