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Cache child sibling lookups

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Removes catastrophically quadratic behavior on nodes with very many siblings.
This commit is contained in:
Łukasz Langa 2018-06-09 18:50:20 -07:00
parent ec31ee967d
commit 2228890d62
2 changed files with 29 additions and 15 deletions
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2
README.md
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@ -814,6 +814,8 @@ More details can be found in [CONTRIBUTING](CONTRIBUTING.md).
* fixed unnecessary slowdown when long list literals where found in a file * fixed unnecessary slowdown when long list literals where found in a file
* fixed unnecessary slowdown on AST nodes with very many siblings
### 18.6b2 ### 18.6b2

42
blib2to3/pytree.py
View File

@ -115,8 +115,9 @@ def replace(self, new):
else: else:
l_children.append(ch) l_children.append(ch)
assert found, (self.children, self, new) assert found, (self.children, self, new)
self.parent.changed()
self.parent.children = l_children self.parent.children = l_children
self.parent.changed()
self.parent.invalidate_sibling_maps()
for x in new: for x in new:
x.parent = self.parent x.parent = self.parent
self.parent = None self.parent = None
@ -143,8 +144,9 @@ def remove(self):
if self.parent: if self.parent:
for i, node in enumerate(self.parent.children): for i, node in enumerate(self.parent.children):
if node is self: if node is self:
self.parent.changed()
del self.parent.children[i] del self.parent.children[i]
self.parent.changed()
self.parent.invalidate_sibling_maps()
self.parent = None self.parent = None
return i return i
@ -157,13 +159,9 @@ def next_sibling(self):
if self.parent is None: if self.parent is None:
return None return None
# Can't use index(); we need to test by identity if self.parent.next_sibling_map is None:
for i, child in enumerate(self.parent.children): self.parent.update_sibling_maps()
if child is self: return self.parent.next_sibling_map[id(self)]
try:
return self.parent.children[i+1]
except IndexError:
return None
@property @property
def prev_sibling(self): def prev_sibling(self):
@ -174,12 +172,9 @@ def prev_sibling(self):
if self.parent is None: if self.parent is None:
return None return None
# Can't use index(); we need to test by identity if self.parent.prev_sibling_map is None:
for i, child in enumerate(self.parent.children): self.parent.update_sibling_maps()
if child is self: return self.parent.prev_sibling_map[id(self)]
if i == 0:
return None
return self.parent.children[i-1]
def leaves(self): def leaves(self):
for child in self.children: for child in self.children:
@ -226,6 +221,7 @@ def __init__(self,type, children,
for ch in self.children: for ch in self.children:
assert ch.parent is None, repr(ch) assert ch.parent is None, repr(ch)
ch.parent = self ch.parent = self
self.invalidate_sibling_maps()
if prefix is not None: if prefix is not None:
self.prefix = prefix self.prefix = prefix
if fixers_applied: if fixers_applied:
@ -294,6 +290,7 @@ def set_child(self, i, child):
self.children[i].parent = None self.children[i].parent = None
self.children[i] = child self.children[i] = child
self.changed() self.changed()
self.invalidate_sibling_maps()
def insert_child(self, i, child): def insert_child(self, i, child):
""" """
@ -303,6 +300,7 @@ def insert_child(self, i, child):
child.parent = self child.parent = self
self.children.insert(i, child) self.children.insert(i, child)
self.changed() self.changed()
self.invalidate_sibling_maps()
def append_child(self, child): def append_child(self, child):
""" """
@ -312,7 +310,21 @@ def append_child(self, child):
child.parent = self child.parent = self
self.children.append(child) self.children.append(child)
self.changed() self.changed()
self.invalidate_sibling_maps()
def invalidate_sibling_maps(self):
self.prev_sibling_map = None
self.next_sibling_map = None
def update_sibling_maps(self):
self.prev_sibling_map = _prev = {}
self.next_sibling_map = _next = {}
previous = None
for current in self.children:
_prev[id(current)] = previous
_next[id(previous)] = current
previous = current
_next[id(current)] = None
class Leaf(Base): class Leaf(Base):