bdiff: don't check border condition in loop
This is pretty much a copy of d500ddae7494, just to a different loop.
The condition `p == plast` (`plast == a + len - 1`) was only true on
the final iteration of the loop. So it was wasteful to check for it
on every iteration. We decrease the iteration count by 1 and add an
explicit check for `p == plast` after the loop.
Again, we see modest wins.
From the mozilla-unified repository:
$ perfbdiff -m 3041e4d59df2
! wall 0.035502 comb 0.040000 user 0.040000 sys 0.000000 (best of 100)
! wall 0.030480 comb 0.030000 user 0.030000 sys 0.000000 (best of 100)
$ perfbdiff 0e9928989e9c --alldata --count 100
! wall 4.097394 comb 4.100000 user 4.100000 sys 0.000000 (best of 3)
! wall 3.597798 comb 3.600000 user 3.600000 sys 0.000000 (best of 3)
The 2nd example throws a total of ~3.3GB of data at bdiff. This
change increases the throughput from ~811 MB/s to ~924 MB/s.
from __future__ import print_function
from mercurial import demandimport
demandimport.enable()
import os
import subprocess
import sys
# Only run if demandimport is allowed
if subprocess.call(['python', '%s/hghave' % os.environ['TESTDIR'],
'demandimport']):
sys.exit(80)
if os.name != 'nt':
try:
import distutils.msvc9compiler
print('distutils.msvc9compiler needs to be an immediate '
'importerror on non-windows platforms')
distutils.msvc9compiler
except ImportError:
pass
import re
rsub = re.sub
def f(obj):
l = repr(obj)
l = rsub("0x[0-9a-fA-F]+", "0x?", l)
l = rsub("from '.*'", "from '?'", l)
l = rsub("'<[a-z]*>'", "'<whatever>'", l)
return l
import os
print("os =", f(os))
print("os.system =", f(os.system))
print("os =", f(os))
from mercurial import util
print("util =", f(util))
print("util.system =", f(util.system))
print("util =", f(util))
print("util.system =", f(util.system))
from mercurial import hgweb
print("hgweb =", f(hgweb))
print("hgweb_mod =", f(hgweb.hgweb_mod))
print("hgweb =", f(hgweb))
import re as fred
print("fred =", f(fred))
import sys as re
print("re =", f(re))
print("fred =", f(fred))
print("fred.sub =", f(fred.sub))
print("fred =", f(fred))
print("re =", f(re))
print("re.stderr =", f(re.stderr))
print("re =", f(re))
import contextlib
print("contextlib =", f(contextlib))
try:
from contextlib import unknownattr
print('no demandmod should be created for attribute of non-package '
'module:\ncontextlib.unknownattr =', f(unknownattr))
except ImportError as inst:
print('contextlib.unknownattr = ImportError: %s' % inst)
demandimport.disable()
os.environ['HGDEMANDIMPORT'] = 'disable'
# this enable call should not actually enable demandimport!
demandimport.enable()
from mercurial import node
print("node =", f(node))