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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 | 85cba926cb59 |
children | 4b0fc75f9403 |
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#!/usr/bin/env python # # An example hgweb CGI script, edit as necessary # See also http://mercurial.selenic.com/wiki/PublishingRepositories # Path to repo or hgweb config to serve (see 'hg help hgweb') config = "/path/to/repo/or/config" # Uncomment and adjust if Mercurial is not installed system-wide # (consult "installed modules" path from 'hg debuginstall'): #import sys; sys.path.insert(0, "/path/to/python/lib") # Uncomment to send python tracebacks to the browser if an error occurs: #import cgitb; cgitb.enable() from mercurial import demandimport; demandimport.enable() from mercurial.hgweb import hgweb, wsgicgi application = hgweb(config) wsgicgi.launch(application)