Mercurial > hg
view tests/test-bdiff.py.out @ 17970:0b03454abae7
ancestor: faster algorithm for difference of ancestor sets
One of the major reasons rebase is slow in large repositories is
the computation of the detach set: the set of ancestors of the
changesets to rebase not in the destination parent. This is currently
done via a revset that does two walks all the way to the root of
the DAG. Instead of doing that, to find ancestors of a set <revs>
not in another set <common> we walk up the tree in reverse revision
number order, maintaining sets of nodes visited from <revs>, <common>
or both.
For the common case where the sets are close both topologically and
in revision number (relative to repository size), this has been
found to speed up rebase by around 15-20%. When the nodes are farther
apart and the DAG is highly branching, it is harder to say which
would win.
Here's how long computing the detach set takes in a linear repository
with over 400000 changesets, rebasing near tip:
Rebasing across 4 changesets
Revset method: 2.2s
New algorithm: 0.00015s
Rebasing across 250 changesets
Revset method: 2.2s
New algorithm: 0.00069s
Rebasing across 10000 changesets
Revset method: 2.4s
New algorithm: 0.019s
author | Siddharth Agarwal <sid0@fb.com> |
---|---|
date | Mon, 26 Nov 2012 11:46:51 -0800 |
parents | eeac5e179243 |
children | 9a8363d23419 |
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*** 'a\nc\n\n\n\n' 'a\nb\n\n\n' *** 'a\nb\nc\n' 'a\nc\n' *** '' '' *** 'a\nb\nc' 'a\nb\nc' *** 'a\nb\nc\nd\n' 'a\nd\n' *** 'a\nb\nc\nd\n' 'a\nc\ne\n' *** 'a\nb\nc\n' 'a\nc\n' *** 'a\n' 'c\na\nb\n' *** 'a\n' '' *** 'a\n' 'b\nc\n' *** 'a\n' 'c\na\n' *** '' 'adjfkjdjksdhfksj' *** '' 'ab' *** '' 'abc' *** 'a' 'a' *** 'ab' 'ab' *** 'abc' 'abc' *** 'a\n' 'a\n' *** 'a\nb' 'a\nb' 6 6 'y\n\n' 6 6 'y\n\n' 9 9 'y\n\n' done done