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.
# Copyright (c) 2016-present, Gregory Szorc
# All rights reserved.
#
# This software may be modified and distributed under the terms
# of the BSD license. See the LICENSE file for details.
import os
from distutils.extension import Extension
zstd_sources = ['zstd/%s' % p for p in (
'common/entropy_common.c',
'common/error_private.c',
'common/fse_decompress.c',
'common/xxhash.c',
'common/zstd_common.c',
'compress/fse_compress.c',
'compress/huf_compress.c',
'compress/zbuff_compress.c',
'compress/zstd_compress.c',
'decompress/huf_decompress.c',
'decompress/zbuff_decompress.c',
'decompress/zstd_decompress.c',
'dictBuilder/divsufsort.c',
'dictBuilder/zdict.c',
)]
zstd_includes = [
'c-ext',
'zstd',
'zstd/common',
'zstd/compress',
'zstd/decompress',
'zstd/dictBuilder',
]
ext_sources = [
'zstd.c',
'c-ext/compressiondict.c',
'c-ext/compressobj.c',
'c-ext/compressor.c',
'c-ext/compressoriterator.c',
'c-ext/compressionparams.c',
'c-ext/compressionwriter.c',
'c-ext/constants.c',
'c-ext/decompressobj.c',
'c-ext/decompressor.c',
'c-ext/decompressoriterator.c',
'c-ext/decompressionwriter.c',
'c-ext/dictparams.c',
]
def get_c_extension(name='zstd'):
"""Obtain a distutils.extension.Extension for the C extension."""
root = os.path.abspath(os.path.dirname(__file__))
sources = [os.path.join(root, p) for p in zstd_sources + ext_sources]
include_dirs = [os.path.join(root, d) for d in zstd_includes]
# TODO compile with optimizations.
return Extension(name, sources,
include_dirs=include_dirs)