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.

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#!/usr/bin/env python

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from __future__ import absolute_import

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__doc__ = """Same as `echo a >> b`, but ensures a changed mtime of b.

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Without this svn will not detect workspace changes."""

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import os

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import sys

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text = sys.argv[1]

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fname = sys.argv[2]

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f = open(fname, "ab")

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try:

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    before = os.fstat(f.fileno()).st_mtime

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    f.write(text)

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    f.write("\n")

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finally:

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    f.close()

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inc = 1

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now = os.stat(fname).st_mtime

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while now == before:

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    t = now + inc

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    inc += 1

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    os.utime(fname, (t, t))

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    now = os.stat(fname).st_mtime

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