tests/revlog-formatv0.py

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.

#!/usr/bin/env python
# Copyright 2010 Intevation GmbH
# Author(s):
# Thomas Arendsen Hein <[e-mail]>
#
# This software may be used and distributed according to the terms of the
# GNU General Public License version 2 or any later version.

"""Create a Mercurial repository in revlog format 0

changeset:   0:a1ef0b125355
tag:         tip
user:        user
date:        Thu Jan 01 00:00:00 1970 +0000
files:       empty
description:
empty file
"""

from __future__ import absolute_import
import os
import sys

files = [
    ('formatv0/.hg/00changelog.i',
     '000000000000004400000000000000000000000000000000000000'
     '000000000000000000000000000000000000000000000000000000'
     '0000a1ef0b125355d27765928be600cfe85784284ab3'),
    ('formatv0/.hg/00changelog.d',
     '756163613935613961356635353036303562366138343738336237'
     '61623536363738616436356635380a757365720a3020300a656d70'
     '74790a0a656d7074792066696c65'),
    ('formatv0/.hg/00manifest.i',
     '000000000000003000000000000000000000000000000000000000'
     '000000000000000000000000000000000000000000000000000000'
     '0000aca95a9a5f550605b6a84783b7ab56678ad65f58'),
    ('formatv0/.hg/00manifest.d',
     '75656d707479006238306465356431333837353835343163356630'
     '35323635616431343461623966613836643164620a'),
    ('formatv0/.hg/data/empty.i',
     '000000000000000000000000000000000000000000000000000000'
     '000000000000000000000000000000000000000000000000000000'
     '0000b80de5d138758541c5f05265ad144ab9fa86d1db'),
    ('formatv0/.hg/data/empty.d',
     ''),
]

def makedirs(name):
    """recursive directory creation"""
    parent = os.path.dirname(name)
    if parent:
        makedirs(parent)
    os.mkdir(name)

makedirs(os.path.join(*'formatv0/.hg/data'.split('/')))

for name, data in files:
    f = open(name, 'wb')
    f.write(data.decode('hex'))
    f.close()

sys.exit(0)