Mercurial > hg > mercurial-crew-with-dirclash
view comparison.txt @ 373:67081329d49a
Change the size of the short hash representation
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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
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author | mpm@selenic.com |
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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