bdiff: balance recursion to avoid quadratic behavior (issue4704)
For highly structured files like JSON or XML dumps with large numbers
of duplicate lines (eg braces) and isolated matching lines, bdiff
could find large numbers of equally good spans. Because it prefers
earlier matches, this would result in pathologically unbalance
recursion that resulted in quadratic performance.
This patch makes it prefer matches closer to the middle that tend to
balance recursion. This change improves the speed of a pathological
test case from 1100s to 9s.
Included is a smaller test that has a roughly 50x safety margin on the
performance it accepts. It's likely to fail on pure builds because
difflib also has a recursion-balancing problem.
Setup
$ cat <<EOF >> $HGRCPATH
> [color]
> mode = ansi
> [extensions]
> color =
> EOF
$ hg init repo
$ cd repo
$ cat > a <<EOF
> c
> c
> a
> a
> b
> a
> a
> c
> c
> EOF
$ hg ci -Am adda
adding a
$ cat > a <<EOF
> c
> c
> a
> a
> dd
> a
> a
> c
> c
> EOF
default context
$ hg diff --nodates --color=always
\x1b[0;1mdiff -r cf9f4ba66af2 a\x1b[0m (esc)
\x1b[0;31;1m--- a/a\x1b[0m (esc)
\x1b[0;32;1m+++ b/a\x1b[0m (esc)
\x1b[0;35m@@ -2,7 +2,7 @@\x1b[0m (esc)
c
a
a
\x1b[0;31m-b\x1b[0m (esc)
\x1b[0;32m+dd\x1b[0m (esc)
a
a
c
--unified=2
$ hg diff --nodates -U 2 --color=always
\x1b[0;1mdiff -r cf9f4ba66af2 a\x1b[0m (esc)
\x1b[0;31;1m--- a/a\x1b[0m (esc)
\x1b[0;32;1m+++ b/a\x1b[0m (esc)
\x1b[0;35m@@ -3,5 +3,5 @@\x1b[0m (esc)
a
a
\x1b[0;31m-b\x1b[0m (esc)
\x1b[0;32m+dd\x1b[0m (esc)
a
a
diffstat
$ hg diff --stat --color=always
a | 2 \x1b[0;32m+\x1b[0m\x1b[0;31m-\x1b[0m (esc)
1 files changed, 1 insertions(+), 1 deletions(-)
$ cat <<EOF >> $HGRCPATH
> record =
> [ui]
> interactive = true
> [diff]
> git = True
> EOF
#if execbit
record
$ chmod +x a
$ hg record --color=always -m moda a <<EOF
> y
> y
> EOF
\x1b[0;1mdiff --git a/a b/a\x1b[0m (esc)
\x1b[0;36;1mold mode 100644\x1b[0m (esc)
\x1b[0;36;1mnew mode 100755\x1b[0m (esc)
1 hunks, 1 lines changed
\x1b[0;33mexamine changes to 'a'? [Ynesfdaq?]\x1b[0m y (esc)
\x1b[0;35m@@ -2,7 +2,7 @@ c\x1b[0m (esc)
c
a
a
\x1b[0;31m-b\x1b[0m (esc)
\x1b[0;32m+dd\x1b[0m (esc)
a
a
c
\x1b[0;33mrecord this change to 'a'? [Ynesfdaq?]\x1b[0m y (esc)
$ echo "[extensions]" >> $HGRCPATH
$ echo "mq=" >> $HGRCPATH
$ hg rollback
repository tip rolled back to revision 0 (undo commit)
working directory now based on revision 0
qrecord
$ hg qrecord --color=always -m moda patch <<EOF
> y
> y
> EOF
\x1b[0;1mdiff --git a/a b/a\x1b[0m (esc)
\x1b[0;36;1mold mode 100644\x1b[0m (esc)
\x1b[0;36;1mnew mode 100755\x1b[0m (esc)
1 hunks, 1 lines changed
\x1b[0;33mexamine changes to 'a'? [Ynesfdaq?]\x1b[0m y (esc)
\x1b[0;35m@@ -2,7 +2,7 @@ c\x1b[0m (esc)
c
a
a
\x1b[0;31m-b\x1b[0m (esc)
\x1b[0;32m+dd\x1b[0m (esc)
a
a
c
\x1b[0;33mrecord this change to 'a'? [Ynesfdaq?]\x1b[0m y (esc)
$ hg qpop -a
popping patch
patch queue now empty
#endif
issue3712: test colorization of subrepo diff
$ hg init sub
$ echo b > sub/b
$ hg -R sub commit -Am 'create sub'
adding b
$ echo 'sub = sub' > .hgsub
$ hg add .hgsub
$ hg commit -m 'add subrepo sub'
$ echo aa >> a
$ echo bb >> sub/b
$ hg diff --color=always -S
\x1b[0;1mdiff --git a/a b/a\x1b[0m (esc)
\x1b[0;31;1m--- a/a\x1b[0m (esc)
\x1b[0;32;1m+++ b/a\x1b[0m (esc)
\x1b[0;35m@@ -7,3 +7,4 @@\x1b[0m (esc)
a
c
c
\x1b[0;32m+aa\x1b[0m (esc)
\x1b[0;1mdiff --git a/sub/b b/sub/b\x1b[0m (esc)
\x1b[0;31;1m--- a/sub/b\x1b[0m (esc)
\x1b[0;32;1m+++ b/sub/b\x1b[0m (esc)
\x1b[0;35m@@ -1,1 +1,2 @@\x1b[0m (esc)
b
\x1b[0;32m+bb\x1b[0m (esc)
test tabs
$ cat >> a <<EOF
> one tab
> two tabs
> end tab
> mid tab
> all tabs
> EOF
$ hg diff --nodates --color=always
\x1b[0;1mdiff --git a/a b/a\x1b[0m (esc)
\x1b[0;31;1m--- a/a\x1b[0m (esc)
\x1b[0;32;1m+++ b/a\x1b[0m (esc)
\x1b[0;35m@@ -7,3 +7,9 @@\x1b[0m (esc)
a
c
c
\x1b[0;32m+aa\x1b[0m (esc)
\x1b[0;32m+\x1b[0m \x1b[0;32mone tab\x1b[0m (esc)
\x1b[0;32m+\x1b[0m \x1b[0;32mtwo tabs\x1b[0m (esc)
\x1b[0;32m+end tab\x1b[0m\x1b[0;1;41m \x1b[0m (esc)
\x1b[0;32m+mid\x1b[0m \x1b[0;32mtab\x1b[0m (esc)
\x1b[0;32m+\x1b[0m \x1b[0;32mall\x1b[0m \x1b[0;32mtabs\x1b[0m\x1b[0;1;41m \x1b[0m (esc)
$ echo "[color]" >> $HGRCPATH
$ echo "diff.tab = bold magenta" >> $HGRCPATH
$ hg diff --nodates --color=always
\x1b[0;1mdiff --git a/a b/a\x1b[0m (esc)
\x1b[0;31;1m--- a/a\x1b[0m (esc)
\x1b[0;32;1m+++ b/a\x1b[0m (esc)
\x1b[0;35m@@ -7,3 +7,9 @@\x1b[0m (esc)
a
c
c
\x1b[0;32m+aa\x1b[0m (esc)
\x1b[0;32m+\x1b[0m\x1b[0;1;35m \x1b[0m\x1b[0;32mone tab\x1b[0m (esc)
\x1b[0;32m+\x1b[0m\x1b[0;1;35m \x1b[0m\x1b[0;32mtwo tabs\x1b[0m (esc)
\x1b[0;32m+end tab\x1b[0m\x1b[0;1;41m \x1b[0m (esc)
\x1b[0;32m+mid\x1b[0m\x1b[0;1;35m \x1b[0m\x1b[0;32mtab\x1b[0m (esc)
\x1b[0;32m+\x1b[0m\x1b[0;1;35m \x1b[0m\x1b[0;32mall\x1b[0m\x1b[0;1;35m \x1b[0m\x1b[0;32mtabs\x1b[0m\x1b[0;1;41m \x1b[0m (esc)
$ cd ..