Mercurial > hg
view mercurial/hbisect.py @ 29322:66dbdd3cc2b9 stable
bdiff: extend matches across popular lines
For very large diffs that have large numbers of identical lines (JSON
dumps) that also have large blocks of identical text, bdiff could become
confused about which block matches which because it can only match
very limited regions. The result is very large diffs for small sets of edits.
The earlier recursion rebalancing fix made this behavior more frequent because
it's now more prone to match block 1 to block 2. One frequent user of
large JSON files reported being unable to pass the resulting diffs
through their code review system.
Prior to this change, bdiff would calculate the length of a match at
(i, j) as 1 + length found at (i-1, j-1). With large number of popular
(ignored) lines, this often meant matches couldn't be extended
backwards at all and thus all matching regions were very small.
Disabling the popularity threshold is not an option because it brings
back quadratic behavior.
Instead, we extend a match backwards until we either found a previously
discovered match or we find a mismatching line. This thus successfully
bridges over any popular lines inside and before a matching region.
The larger regions then significant reduce the probability of confusion.
author | Matt Mackall <mpm@selenic.com> |
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date | Thu, 02 Jun 2016 17:09:06 -0500 |
parents | 9b8a5c6ac176 |
children | ee21ed7fc7a2 |
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# changelog bisection for mercurial # # Copyright 2007 Matt Mackall # Copyright 2005, 2006 Benoit Boissinot <benoit.boissinot@ens-lyon.org> # # Inspired by git bisect, extension skeleton taken from mq.py. # # This software may be used and distributed according to the terms of the # GNU General Public License version 2 or any later version. from __future__ import absolute_import import collections from .i18n import _ from .node import ( hex, short, ) from . import ( error, ) def bisect(changelog, state): """find the next node (if any) for testing during a bisect search. returns a (nodes, number, good) tuple. 'nodes' is the final result of the bisect if 'number' is 0. Otherwise 'number' indicates the remaining possible candidates for the search and 'nodes' contains the next bisect target. 'good' is True if bisect is searching for a first good changeset, False if searching for a first bad one. """ clparents = changelog.parentrevs skip = set([changelog.rev(n) for n in state['skip']]) def buildancestors(bad, good): # only the earliest bad revision matters badrev = min([changelog.rev(n) for n in bad]) goodrevs = [changelog.rev(n) for n in good] goodrev = min(goodrevs) # build visit array ancestors = [None] * (len(changelog) + 1) # an extra for [-1] # set nodes descended from goodrevs for rev in goodrevs: ancestors[rev] = [] for rev in changelog.revs(goodrev + 1): for prev in clparents(rev): if ancestors[prev] == []: ancestors[rev] = [] # clear good revs from array for rev in goodrevs: ancestors[rev] = None for rev in changelog.revs(len(changelog), goodrev): if ancestors[rev] is None: for prev in clparents(rev): ancestors[prev] = None if ancestors[badrev] is None: return badrev, None return badrev, ancestors good = False badrev, ancestors = buildancestors(state['bad'], state['good']) if not ancestors: # looking for bad to good transition? good = True badrev, ancestors = buildancestors(state['good'], state['bad']) bad = changelog.node(badrev) if not ancestors: # now we're confused if (len(state['bad']) == 1 and len(state['good']) == 1 and state['bad'] != state['good']): raise error.Abort(_("starting revisions are not directly related")) raise error.Abort(_("inconsistent state, %s:%s is good and bad") % (badrev, short(bad))) # build children dict children = {} visit = collections.deque([badrev]) candidates = [] while visit: rev = visit.popleft() if ancestors[rev] == []: candidates.append(rev) for prev in clparents(rev): if prev != -1: if prev in children: children[prev].append(rev) else: children[prev] = [rev] visit.append(prev) candidates.sort() # have we narrowed it down to one entry? # or have all other possible candidates besides 'bad' have been skipped? tot = len(candidates) unskipped = [c for c in candidates if (c not in skip) and (c != badrev)] if tot == 1 or not unskipped: return ([changelog.node(rev) for rev in candidates], 0, good) perfect = tot // 2 # find the best node to test best_rev = None best_len = -1 poison = set() for rev in candidates: if rev in poison: # poison children poison.update(children.get(rev, [])) continue a = ancestors[rev] or [rev] ancestors[rev] = None x = len(a) # number of ancestors y = tot - x # number of non-ancestors value = min(x, y) # how good is this test? if value > best_len and rev not in skip: best_len = value best_rev = rev if value == perfect: # found a perfect candidate? quit early break if y < perfect and rev not in skip: # all downhill from here? # poison children poison.update(children.get(rev, [])) continue for c in children.get(rev, []): if ancestors[c]: ancestors[c] = list(set(ancestors[c] + a)) else: ancestors[c] = a + [c] assert best_rev is not None best_node = changelog.node(best_rev) return ([best_node], tot, good) def load_state(repo): state = {'current': [], 'good': [], 'bad': [], 'skip': []} for l in repo.vfs.tryreadlines("bisect.state"): kind, node = l[:-1].split() node = repo.lookup(node) if kind not in state: raise error.Abort(_("unknown bisect kind %s") % kind) state[kind].append(node) return state def save_state(repo, state): f = repo.vfs("bisect.state", "w", atomictemp=True) with repo.wlock(): for kind in sorted(state): for node in state[kind]: f.write("%s %s\n" % (kind, hex(node))) f.close() def get(repo, status): """ Return a list of revision(s) that match the given status: - ``good``, ``bad``, ``skip``: csets explicitly marked as good/bad/skip - ``goods``, ``bads`` : csets topologically good/bad - ``range`` : csets taking part in the bisection - ``pruned`` : csets that are goods, bads or skipped - ``untested`` : csets whose fate is yet unknown - ``ignored`` : csets ignored due to DAG topology - ``current`` : the cset currently being bisected """ state = load_state(repo) if status in ('good', 'bad', 'skip', 'current'): return map(repo.changelog.rev, state[status]) else: # In the following sets, we do *not* call 'bisect()' with more # than one level of recursion, because that can be very, very # time consuming. Instead, we always develop the expression as # much as possible. # 'range' is all csets that make the bisection: # - have a good ancestor and a bad descendant, or conversely # that's because the bisection can go either way range = '( bisect(bad)::bisect(good) | bisect(good)::bisect(bad) )' _t = repo.revs('bisect(good)::bisect(bad)') # The sets of topologically good or bad csets if len(_t) == 0: # Goods are topologically after bads goods = 'bisect(good)::' # Pruned good csets bads = '::bisect(bad)' # Pruned bad csets else: # Goods are topologically before bads goods = '::bisect(good)' # Pruned good csets bads = 'bisect(bad)::' # Pruned bad csets # 'pruned' is all csets whose fate is already known: good, bad, skip skips = 'bisect(skip)' # Pruned skipped csets pruned = '( (%s) | (%s) | (%s) )' % (goods, bads, skips) # 'untested' is all cset that are- in 'range', but not in 'pruned' untested = '( (%s) - (%s) )' % (range, pruned) # 'ignored' is all csets that were not used during the bisection # due to DAG topology, but may however have had an impact. # E.g., a branch merged between bads and goods, but whose branch- # point is out-side of the range. iba = '::bisect(bad) - ::bisect(good)' # Ignored bads' ancestors iga = '::bisect(good) - ::bisect(bad)' # Ignored goods' ancestors ignored = '( ( (%s) | (%s) ) - (%s) )' % (iba, iga, range) if status == 'range': return repo.revs(range) elif status == 'pruned': return repo.revs(pruned) elif status == 'untested': return repo.revs(untested) elif status == 'ignored': return repo.revs(ignored) elif status == "goods": return repo.revs(goods) elif status == "bads": return repo.revs(bads) else: raise error.ParseError(_('invalid bisect state')) def label(repo, node): rev = repo.changelog.rev(node) # Try explicit sets if rev in get(repo, 'good'): # i18n: bisect changeset status return _('good') if rev in get(repo, 'bad'): # i18n: bisect changeset status return _('bad') if rev in get(repo, 'skip'): # i18n: bisect changeset status return _('skipped') if rev in get(repo, 'untested') or rev in get(repo, 'current'): # i18n: bisect changeset status return _('untested') if rev in get(repo, 'ignored'): # i18n: bisect changeset status return _('ignored') # Try implicit sets if rev in get(repo, 'goods'): # i18n: bisect changeset status return _('good (implicit)') if rev in get(repo, 'bads'): # i18n: bisect changeset status return _('bad (implicit)') return None def shortlabel(label): if label: return label[0].upper() return None