comparison mercurial/patch.py @ 46020:210f9b8d7bbd stable

diff: do not concatenate immutable bytes while building a/b bodies (issue6445)

Use bytearray instead. I don't know what's changed since Python 2, but bytes
concatenation is 100x slow on Python 3.

  % python2.7 -m timeit -s "s = b''" "for i in range(10000): s += b'line'"
  1000 loops, best of 3: 321 usec per loop

  % python3.9 -m timeit -s "s = b''" "for i in range(10000): s += b'line'"
  5 loops, best of 5: 39.2 msec per loop

Benchmark using tailwind.css (measuring the fast path, a is empty):

  % HGRCPATH=/dev/null python2.7 ./hg log -R /tmp/issue6445 -p --time \
  --color=always --config diff.word-diff=true >/dev/null
  (prev) time: real 1.580 secs (user 1.560+0.000 sys 0.020+0.000)
  (this) time: real 1.610 secs (user 1.570+0.000 sys 0.030+0.000)

  % HGRCPATH=/dev/null python3.9 ./hg log -R /tmp/issue6445 -p --time \
  --color=always --config diff.word-diff=true >/dev/null
  (prev) time: real 114.500 secs (user 114.460+0.000 sys 0.030+0.000)
  (this) time: real 2.180 secs (user 2.140+0.000 sys 0.040+0.000)

Benchmark using random tabular text data (not the fast path):

  % dd if=/dev/urandom bs=1k count=1000 | hexdump -v -e '16/1 "%3u," "\n"' > ttf
  % hg ci -ma
  % dd if=/dev/urandom bs=1k count=1000 | hexdump -v -e '16/1 "%3u," "\n"' > ttf
  % hg ci -mb

  % HGRCPATH=/dev/null python2.7 ./hg log -R /tmp/issue6445 -p --time \
  --color=always --config diff.word-diff=true >/dev/null
  (prev) time: real 3.240 secs (user 3.040+0.000 sys 0.200+0.000
  (this) time: real 3.230 secs (user 3.070+0.000 sys 0.160+0.000)

  % HGRCPATH=/dev/null python3.9 ./hg log -R /tmp/issue6445 -p --time \
  --color=always --config diff.word-diff=true >/dev/null
  (prev) time: real 44.130 secs (user 43.850+0.000 sys 0.270+0.000)
  (this) time: real 4.170 secs (user 3.850+0.000 sys 0.310+0.000)

46019:fdd54a876213

def diffsinglehunkinline(hunklines):
    """yield tokens for a list of lines in a single hunk, with inline colors"""
    # prepare deleted, and inserted content
    a = b''
    b = b''
    for line in hunklines:
        if line[0:1] == b'-':
            a += line[1:]
        elif line[0:1] == b'+':
            b += line[1:]

    if not a or not b:
        for t in diffsinglehunk(hunklines):
            yield t
        return
    # re-split the content into words
    al = wordsplitter.findall(a)
    bl = wordsplitter.findall(b)
    # re-arrange the words to lines since the diff algorithm is line-based
    aln = [s if s == b'\n' else s + b'\n' for s in al]
    bln = [s if s == b'\n' else s + b'\n' for s in bl]
    an = b''.join(aln)
    bn = b''.join(bln)

46020:210f9b8d7bbd

def diffsinglehunkinline(hunklines):
    """yield tokens for a list of lines in a single hunk, with inline colors"""
    # prepare deleted, and inserted content
    a = bytearray()
    b = bytearray()
    for line in hunklines:
        if line[0:1] == b'-':
            a += line[1:]
        elif line[0:1] == b'+':
            b += line[1:]

    if not a or not b:
        for t in diffsinglehunk(hunklines):
            yield t
        return
    # re-split the content into words
    al = wordsplitter.findall(bytes(a))
    bl = wordsplitter.findall(bytes(b))
    # re-arrange the words to lines since the diff algorithm is line-based
    aln = [s if s == b'\n' else s + b'\n' for s in al]
    bln = [s if s == b'\n' else s + b'\n' for s in bl]
    an = b''.join(aln)
    bn = b''.join(bln)