On Tue, Nov 15, 2016 at 09:57:08PM +0100, Mads Kiilerich wrote:
> # HG changeset patch
> # User Mads Kiilerich <mad...@unity3d.com>
> # Date 1479243409 -3600
> # Tue Nov 15 21:56:49 2016 +0100
> # Node ID efa30442953a6e1f096f8833c4ee8047375600d6
> # Parent e022e995415bd48ffe6d4d03dc97b99dd547cde1
> bdiff: give slight preference to removing trailing lines
My own cursory perfbdiff runs suggest this is a perf wash (using
`perfbdiff -m 3041e4d59df2` in the mozilla repo). Queued. Thanks!
>
> [This change could be folded into the previous changeset to minimize the repo
> churn ...]
>
> Similar to the previous change, introduce an exception to the general
> preference for matches in the middle of bdiff ranges: If the best match on the
> B side starts at the beginning of the bdiff range, don't aim for the
> middle-most A side match but for the earliest.
>
> New (later) matches on the A side will only be considered better if the
> corresponding match on the B side *not* is at the beginning of the range.
> Thus, if the best (middle-most) match on the B side turns out to be at the
> beginning of the range, the earliest match on the A side will be used.
>
> The bundle size for 4.0 (hg bundle --base null -r 4.0 x.hg) happens to go from
> 22807275 to 22808120 bytes - a 0.004% increase.
>
> diff --git a/mercurial/bdiff.c b/mercurial/bdiff.c
> --- a/mercurial/bdiff.c
> +++ b/mercurial/bdiff.c
> @@ -184,7 +184,7 @@ static int longest_match(struct bdiff_li
> mj = j;
> mk = k;
> } else if (k == mk) {
> - if (i > mi && i <= half) {
> + if (i > mi && i <= half && j > b1) {
> /* same match but closer to half */
> mi = i;
> mj = j;
> diff --git a/tests/test-bdiff.py b/tests/test-bdiff.py
> --- a/tests/test-bdiff.py
> +++ b/tests/test-bdiff.py
> @@ -88,7 +88,7 @@ print("Diff 1 to 3 lines - preference fo
> showdiff('a\n', 'a\n' * 3)
> print("Diff 1 to 5 lines - preference for appending:")
> showdiff('a\n', 'a\n' * 5)
> -print("Diff 3 to 1 lines - preference for balanced recursion:")
> +print("Diff 3 to 1 lines - preference for removing trailing lines:")
> showdiff('a\n' * 3, 'a\n')
> -print("Diff 5 to 1 lines - preference for balanced recursion:")
> +print("Diff 5 to 1 lines - preference for removing trailing lines:")
> showdiff('a\n' * 5, 'a\n')
> diff --git a/tests/test-bdiff.py.out b/tests/test-bdiff.py.out
> --- a/tests/test-bdiff.py.out
> +++ b/tests/test-bdiff.py.out
> @@ -68,17 +68,15 @@ showdiff(
> 'a\na\na\na\na\n'):
> 'a\n'
> 2 2 '' -> 'a\na\na\na\n'
> -Diff 3 to 1 lines - preference for balanced recursion:
> +Diff 3 to 1 lines - preference for removing trailing lines:
> showdiff(
> 'a\na\na\n',
> 'a\n'):
> - 0 2 'a\n' -> ''
> 'a\n'
> - 4 6 'a\n' -> ''
> -Diff 5 to 1 lines - preference for balanced recursion:
> + 2 6 'a\na\n' -> ''
> +Diff 5 to 1 lines - preference for removing trailing lines:
> showdiff(
> 'a\na\na\na\na\n',
> 'a\n'):
> - 0 4 'a\na\n' -> ''
> 'a\n'
> - 6 10 'a\na\n' -> ''
> + 2 10 'a\na\na\na\n' -> ''
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