Hi everybody, Just forwarding some comments from Apfelmus regarding the recent paper by Judah on Darcs patch theory ( http://www.math.ucla.edu/~jjacobson/patch-theory/ )
Thanks, Eric -- Eric Kow <http://www.nltg.brighton.ac.uk/home/Eric.Kow> PGP Key ID: 08AC04F9
--- Begin Message ---Hello Eric,On Tue, Oct 20, 2009 at 21:03:11 +0200, Heinrich Apfelmus wrote:For instance, concerning merges, the following curiosity occurred to me: imagine three people working in parallel and making three patches A,B and C respectively against some common repository R. And now, imaginethe following weird situation:There is a conflict when trying to merge all three patches A,B and C,but you can merge any two of them, i.e. A and B can be merged, B and C can be merged and A and C can be merged.You may be interested in a related (but seemingly different) test for something the OT people call 'convergence'. http://darcs.net/tests/failing-issue1609_ot_convergence.shIt appears to me that, in terms of commutators, this 'convergence' property from OT is to be expressed as follows:patches C, A, B in that order if A B commutes to B' A' and C (AB) commutes to (AB)' C1' and C (B'A') commutes to (B'A')' C2' then (AB)' C1' and (B'A')' C2' should have the same effect In particular, I have chosen C = invert op3 A = op1 B = T(op2,op1) What my curiosity asks is slightly different, namely whether if A B commutes to B' A' and C A commutes to Ac Ca and C B' commutes to B'c Cb then do Ca B or Cb A' actually commute as well?In other words, it asks whether the postulated commutations in the convergence property actually hold. It could well be possible to commute the C past the A and the C past the B' separately, but impossible to commute C past both at the same time.By the way, I would a priori think that the shell script you mentioned should be something likedarcs pull -a --repo Temp S1 darcs pull -a --repo Temp S2 darcs pull -a --repo Temp S3 vs darcs pull -a --repo Temp2 S2 darcs pull -a --repo Temp2 S1 darcs pull -a --repo Temp2 S3and then compare Temp and Temp2 ? But I'm not familiar enough with darcs to judge that.Also : the call for GUIDs is echo'ed in Jean-Phillipe Benardy's FoCAL work as well as the OT researchers' new 'conflict-free' approach, which they have implemented in the form of a hacked up mediawiki. Please have a look at http://wiki.darcs.net/Theory/Bibliography if you're interested :-)Benardy's stuff looks interesting, but it appears that they moved half of the theory into the description of the implementation. :-/ In particular, the representation as multisets ("weights") seems to be a fundamental trick and should be analyzed properly! Why can't people stop to just hack something together? ;-)But yes, I think that GUIDs are the way to go and that commutators are just obscuring the main issues.Regards, apfelmus -- http://apfelmus.nfshost.com
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