bisect: avoid copying ancestor list for non-merge commits
During a bisection, hg needs to compute a list of all ancestors for every
candidate commit. This is accomplished via a bottom-up traversal of the set of
candidates, during which each revision's ancestor list is populated using the
ancestor list of its parent(s). Previously, this involved copying the entire
list, which could be very long in if the bisection range was large.
To help improve this, we can observe that each candidate commit is visited
exactly once, at which point its ancestor list is copied into its children's
lists and then dropped. In the case of non-merge commits, a commit's ancestor
list consists exactly of its parent's list plus itself. This means that we can
trivially reuse the parent's existing list for one of its non-merge children,
which avoids copying entirely if that commit is the parent's only child. This
makes bisections over linear ranges of commits much faster.
During some informal testing in the large publicly-available `mozilla-central`
repository, this noticeably sped up bisections over large ranges of history:
Setup:
$ cd mozilla-central
$ hg bisect --reset
$ hg bisect --good 0
$ hg log -r tip -T '{rev}\n'
628417
Test:
$ time hg bisect --bad tip --noupdate
Before:
real 3m35.927s
user 3m35.553s
sys 0m0.319s
After:
real 1m41.142s
user 1m40.810s
sys 0m0.285s
# similar.py - mechanisms for finding similar files
#
# Copyright 2005-2007 Olivia Mackall <olivia@selenic.com>
#
# This software may be used and distributed according to the terms of the
# GNU General Public License version 2 or any later version.
from .i18n import _
from . import (
mdiff,
)
def _findexactmatches(repo, added, removed):
"""find renamed files that have no changes
Takes a list of new filectxs and a list of removed filectxs, and yields
(before, after) tuples of exact matches.
"""
# Build table of removed files: {hash(fctx.data()): [fctx, ...]}.
# We use hash() to discard fctx.data() from memory.
hashes = {}
progress = repo.ui.makeprogress(
_(b'searching for exact renames'),
total=(len(added) + len(removed)),
unit=_(b'files'),
)
for fctx in removed:
progress.increment()
h = hash(fctx.data())
if h not in hashes:
hashes[h] = [fctx]
else:
hashes[h].append(fctx)
# For each added file, see if it corresponds to a removed file.
for fctx in added:
progress.increment()
adata = fctx.data()
h = hash(adata)
for rfctx in hashes.get(h, []):
# compare between actual file contents for exact identity
if adata == rfctx.data():
yield (rfctx, fctx)
break
# Done
progress.complete()
def _ctxdata(fctx):
# lazily load text
orig = fctx.data()
return orig, mdiff.splitnewlines(orig)
def _score(fctx, otherdata):
orig, lines = otherdata
text = fctx.data()
# mdiff.blocks() returns blocks of matching lines
# count the number of bytes in each
equal = 0
matches = mdiff.blocks(text, orig)
for x1, x2, y1, y2 in matches:
for line in lines[y1:y2]:
equal += len(line)
lengths = len(text) + len(orig)
return equal * 2.0 / lengths
def score(fctx1, fctx2):
return _score(fctx1, _ctxdata(fctx2))
def _findsimilarmatches(repo, added, removed, threshold):
"""find potentially renamed files based on similar file content
Takes a list of new filectxs and a list of removed filectxs, and yields
(before, after, score) tuples of partial matches.
"""
copies = {}
progress = repo.ui.makeprogress(
_(b'searching for similar files'), unit=_(b'files'), total=len(removed)
)
for r in removed:
progress.increment()
data = None
for a in added:
bestscore = copies.get(a, (None, threshold))[1]
if data is None:
data = _ctxdata(r)
myscore = _score(a, data)
if myscore > bestscore:
copies[a] = (r, myscore)
progress.complete()
for dest, v in copies.items():
source, bscore = v
yield source, dest, bscore
def _dropempty(fctxs):
return [x for x in fctxs if x.size() > 0]
def findrenames(repo, added, removed, threshold):
'''find renamed files -- yields (before, after, score) tuples'''
wctx = repo[None]
pctx = wctx.p1()
# Zero length files will be frequently unrelated to each other, and
# tracking the deletion/addition of such a file will probably cause more
# harm than good. We strip them out here to avoid matching them later on.
addedfiles = _dropempty(wctx[fp] for fp in sorted(added))
removedfiles = _dropempty(pctx[fp] for fp in sorted(removed) if fp in pctx)
# Find exact matches.
matchedfiles = set()
for (a, b) in _findexactmatches(repo, addedfiles, removedfiles):
matchedfiles.add(b)
yield (a.path(), b.path(), 1.0)
# If the user requested similar files to be matched, search for them also.
if threshold < 1.0:
addedfiles = [x for x in addedfiles if x not in matchedfiles]
for (a, b, score) in _findsimilarmatches(
repo, addedfiles, removedfiles, threshold
):
yield (a.path(), b.path(), score)