bdiff: early pruning of common prefix before doing expensive computations
It seems quite common that files don't change completely. New lines are often
pretty much appended, and modifications will often only change a small section
of the file which on average will be in the middle.
There can thus be a big win by pruning a common prefix before starting the more
expensive search for longest common substrings.
Worst case, it will scan through a long sequence of similar bytes without
encountering a newline. Splitlines will then have to do the same again ...
twice for each side. If similar lines are found, splitlines will save the
double iteration and hashing of the lines ... plus there will be less lines to
find common substrings in.
This change might in some cases make the algorith pick shorter or less optimal
common substrings. We can't have the cake and eat it.
This make hg --time bundle --base null -r 4.0 go from 14.5 to 15 s - a 3%
increase.
On mozilla-unified:
perfbdiff -m 3041e4d59df2
! wall 0.053088 comb 0.060000 user 0.060000 sys 0.000000 (best of 100) to
! wall 0.024618 comb 0.020000 user 0.020000 sys 0.000000 (best of 116)
perfbdiff 0e9928989e9c --alldata --count 10
! wall 0.702075 comb 0.700000 user 0.700000 sys 0.000000 (best of 15) to
! wall 0.579235 comb 0.580000 user 0.580000 sys 0.000000 (best of 18)
#!/usr/bin/env python
#
# checkseclevel - checking section title levels in each online help document
from __future__ import absolute_import
import optparse
import os
import sys
# import from the live mercurial repo
os.environ['HGMODULEPOLICY'] = 'py'
sys.path.insert(0, "..")
from mercurial import demandimport; demandimport.enable()
from mercurial import (
commands,
extensions,
help,
minirst,
ui as uimod,
)
table = commands.table
helptable = help.helptable
level2mark = ['"', '=', '-', '.', '#']
reservedmarks = ['"']
mark2level = {}
for m, l in zip(level2mark, xrange(len(level2mark))):
if m not in reservedmarks:
mark2level[m] = l
initlevel_topic = 0
initlevel_cmd = 1
initlevel_ext = 1
initlevel_ext_cmd = 3
def showavailables(ui, initlevel):
ui.warn((' available marks and order of them in this help: %s\n') %
(', '.join(['%r' % (m * 4) for m in level2mark[initlevel + 1:]])))
def checkseclevel(ui, doc, name, initlevel):
ui.note(('checking "%s"\n') % name)
blocks, pruned = minirst.parse(doc, 0, ['verbose'])
errorcnt = 0
curlevel = initlevel
for block in blocks:
if block['type'] != 'section':
continue
mark = block['underline']
title = block['lines'][0]
if (mark not in mark2level) or (mark2level[mark] <= initlevel):
ui.warn(('invalid section mark %r for "%s" of %s\n') %
(mark * 4, title, name))
showavailables(ui, initlevel)
errorcnt += 1
continue
nextlevel = mark2level[mark]
if curlevel < nextlevel and curlevel + 1 != nextlevel:
ui.warn(('gap of section level at "%s" of %s\n') %
(title, name))
showavailables(ui, initlevel)
errorcnt += 1
continue
ui.note(('appropriate section level for "%s %s"\n') %
(mark * (nextlevel * 2), title))
curlevel = nextlevel
return errorcnt
def checkcmdtable(ui, cmdtable, namefmt, initlevel):
errorcnt = 0
for k, entry in cmdtable.items():
name = k.split("|")[0].lstrip("^")
if not entry[0].__doc__:
ui.note(('skip checking %s: no help document\n') %
(namefmt % name))
continue
errorcnt += checkseclevel(ui, entry[0].__doc__,
namefmt % name,
initlevel)
return errorcnt
def checkhghelps(ui):
errorcnt = 0
for names, sec, doc in helptable:
if callable(doc):
doc = doc(ui)
errorcnt += checkseclevel(ui, doc,
'%s help topic' % names[0],
initlevel_topic)
errorcnt += checkcmdtable(ui, table, '%s command', initlevel_cmd)
for name in sorted(extensions.enabled().keys() +
extensions.disabled().keys()):
mod = extensions.load(ui, name, None)
if not mod.__doc__:
ui.note(('skip checking %s extension: no help document\n') % name)
continue
errorcnt += checkseclevel(ui, mod.__doc__,
'%s extension' % name,
initlevel_ext)
cmdtable = getattr(mod, 'cmdtable', None)
if cmdtable:
errorcnt += checkcmdtable(ui, cmdtable,
'%s command of ' + name + ' extension',
initlevel_ext_cmd)
return errorcnt
def checkfile(ui, filename, initlevel):
if filename == '-':
filename = 'stdin'
doc = sys.stdin.read()
else:
with open(filename) as fp:
doc = fp.read()
ui.note(('checking input from %s with initlevel %d\n') %
(filename, initlevel))
return checkseclevel(ui, doc, 'input from %s' % filename, initlevel)
def main():
optparser = optparse.OptionParser("""%prog [options]
This checks all help documents of Mercurial (topics, commands,
extensions and commands of them), if no file is specified by --file
option.
""")
optparser.add_option("-v", "--verbose",
help="enable additional output",
action="store_true")
optparser.add_option("-d", "--debug",
help="debug mode",
action="store_true")
optparser.add_option("-f", "--file",
help="filename to read in (or '-' for stdin)",
action="store", default="")
optparser.add_option("-t", "--topic",
help="parse file as help topic",
action="store_const", dest="initlevel", const=0)
optparser.add_option("-c", "--command",
help="parse file as help of core command",
action="store_const", dest="initlevel", const=1)
optparser.add_option("-e", "--extension",
help="parse file as help of extension",
action="store_const", dest="initlevel", const=1)
optparser.add_option("-C", "--extension-command",
help="parse file as help of extension command",
action="store_const", dest="initlevel", const=3)
optparser.add_option("-l", "--initlevel",
help="set initial section level manually",
action="store", type="int", default=0)
(options, args) = optparser.parse_args()
ui = uimod.ui.load()
ui.setconfig('ui', 'verbose', options.verbose, '--verbose')
ui.setconfig('ui', 'debug', options.debug, '--debug')
if options.file:
if checkfile(ui, options.file, options.initlevel):
sys.exit(1)
else:
if checkhghelps(ui):
sys.exit(1)
if __name__ == "__main__":
main()