[PATCH] ancestors: prefetch method outside of the loop

[Pierre-Yves David]

# HG changeset patch
# User Pierre-Yves David <pierre-yves.david at fb.com>
# Date 1434766800 25200
#      Fri Jun 19 19:20:00 2015 -0700
# Node ID a005a978678ae5bbfdf4cf298af5449db5d7d369
# Parent  2748bf78a5bf610da4f2d90fd1eea19a3b360c04
ancestors: prefetch method outside of the loop

15412bba5a68 is yet another example than this is worthwhile when it comes to
performance, we blindly do in for all 'lazyancestors' method.

diff --git a/mercurial/ancestor.py b/mercurial/ancestor.py
--- a/mercurial/ancestor.py
+++ b/mercurial/ancestor.py
@@ -310,19 +310,23 @@ class lazyancestors(object):
         if self._inclusive:
             for rev in revs:
                 yield rev
             seen.update(revs)
 
+
         parentrevs = self._parentrevs
         stoprev = self._stoprev
         visit = collections.deque(revs)
 
+        see = seen.add
+        schedule = visit.append
+
         while visit:
             for parent in parentrevs(visit.popleft()):
                 if parent >= stoprev and parent not in seen:
-                    visit.append(parent)
-                    seen.add(parent)
+                    schedule(parent)
+                    see(parent)
                     yield parent
 
     def __contains__(self, target):
         """Test whether target is an ancestor of self._initrevs."""
         # Trying to do both __iter__ and __contains__ using the same visit
@@ -335,20 +339,21 @@ class lazyancestors(object):
         parentrevs = self._parentrevs
         visit = self._containsvisit
         stoprev = self._stoprev
         heappop = heapq.heappop
         heappush = heapq.heappush
+        see = seen.add
 
         targetseen = False
 
         while visit and -visit[0] > target and not targetseen:
             for parent in parentrevs(-heappop(visit)):
                 if parent < stoprev or parent in seen:
                     continue
                 # We need to make sure we push all parents into the heap so
                 # that we leave it in a consistent state for future calls.
                 heappush(visit, -parent)
-                seen.add(parent)
+                see(parent)
                 if parent == target:
                     targetseen = True
 
         return targetseen