[darcs-users] Colin Walters blogs on Arch changesets vs Darcs

David Roundy droundy at abridgegame.org
Thu Nov 25 12:42:09 UTC 2004

[mixing quotes up a tad...]

On Wed, Nov 24, 2004 at 11:06:26AM -0400, Zooko O'Whielacronx wrote:
> On 2004, Nov 24, at 03:33, Anthony Towns wrote:
> > AIUI, the main reasons darcs doesn't scale well is that it doesn't have
> > great alogrithms for dealing with conflicts (they go
> > exponential)... [CUT]...  But those are "doesn't scale" not "cannot
> > scale", ttbomk.


> No, that's what I thought at first.  But unless you do the other part
> of my sentence which is ellided above -- organize a central single
> person to be the patch-accepter and have that personally manually
> inspect and de-duplicate patches before allowing them into darcsword --
> then you will eventually get two copies or two variants of a patch
> imported from outside-darcs-world to inside-darcs-world.  Inside
> darcsworld, those two patches are like matter and antimatter (hello,
> physics analogies!) -- as soon as they both meet in the same repo then
> that repo will become locked in its O(N^2) merging algorithm until
> someone manually picks it apart and deletes one of the two patches.

This is what Anthony was saying, when he said that darcs "doesn't scale",
but not necesarily "cannot scale".  The merge algorithms definitely need
improvement when there are conflicts.  It's possible that there is no
efficient solution, which would be very sad, but I'm still optimistic that
I'll be able to figure out a more efficient way to do things.

The current (inefficient) algorithms came about because originally I was
overly ambitious, and when my original ideas turned out to be flawed, I
went with an algorithm (based on the original one) which was safe and
correct via a simple modification of the old algorithm.  Dealing with merge
conflicts isn't easy, and for the last year I've been caught up fixing real
David Roundy

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