view comparison.txt @ 373:67081329d49a

Change the size of the short hash representation -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Change the size of the short hash representation First note that this number doesn't really matter, as we always check for ambiguous short hash ids. Here's the math on collision probability: >>> import math >>> def p(f, n): return 1 - (1 / math.exp(n**2/(2*f))) ... >>> p(2**32, 30000.0) 0.09947179164613551 # with 30000 changesets (BKCVS), we have a 9% chance >>> p(2**32, 65000.0) 0.38850881217977273 # and with a full import from BK, we'd have a 39% chance >>> p(2**40, 1e6) 0.36539171908447321 # we'd like to be "safe" for 1M csets, so 40 isn't enough >>> p(2**48, 1e6) 0.001774780051374103 # But 48 looks good >>> p(2**48, 1e7) 0.16275260939624481 >>> p(2**48, 5e6) 0.043437281083569146 >>> p(2**48, 2e6) 0.0070802434913129764 >>> p(2**48, 3e6) 0.01586009440574343 manifest hash: 24d9f928a463f46708b0e11fb781d5a241851424 -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.0 (GNU/Linux) iD8DBQFCsQoMywK+sNU5EO8RAoBBAJwII9GV6dT9QUOYAk3gZGw9z0JvjACfSI4q IFnTu1F7P5OuLelO1GsM8Bs= =CNWk -----END PGP SIGNATURE-----
author mpm@selenic.com
date Wed, 15 Jun 2005 21:11:40 -0800
parents 17e66e1a0382
children 2073e5a71008
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                    Mercurial      git                     BK (*)
storage             revlog delta   compressed revisions    SCCS weave
storage naming      by filename    by revision hash        by filename
merge               file DAGs      changeset DAG           file DAGs?
consistency         SHA1           SHA1                    CRC
signable?           yes            yes                     no       

retrieve file tip   O(1)           O(1)                    O(revs)
add rev             O(1)           O(1)                    O(revs)
find prev file rev  O(1)           O(changesets)           O(revs)
annotate file       O(revs)        O(changesets)           O(revs)
find file changeset O(1)           O(changesets)           ?

checkout            O(files)       O(files)                O(revs)?
commit              O(changes)     O(changes)              ?
                    6 patches/s    6 patches/s             slow
diff working dir    O(changes)     O(changes)              ?
                    < 1s           < 1s                    ?
tree diff revs      O(changes)     O(changes)              ?
                    < 1s           < 1s                    ?
hardlink clone      O(files)       O(revisions)            O(files)

find remote csets   O(log new)     rsync: O(revisions)     ?
                                   git-http: O(changesets)
pull remote csets   O(patch)       O(modified files)       O(patch)

repo growth         O(patch)       O(revisions)            O(patch)
 kernel history     300M           3.5G?                   250M?
lines of code       2500           6500 (+ cogito)         ??

* I've never used BK so this is just guesses