Messages in this thread | | | Date | Thu, 3 May 2001 05:43:49 -0400 | From | "Eric S. Raymond" <> | Subject | Re: Why recovering from broken configs is too hard |
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Alexander Viro <viro@math.psu.edu>: > Assertion: you can split the set of variables into disjoint union of > small subsets X, Y_1,...,Y_m such that each constraint is concerned > only with variables from X and at most one of Y_i. > > IOW, there is a small "core" and for fixed values of core variables > constraints fall into groups, each dealing with its own _small_ > set of variables. > > If that assertion is true the complexity is nowhere near 3^N. > > Eric, you probably have the most accurate information about the > existing constraints. Care to verify the assertion above? I'm > serious - the set of constraints is very far from generic and > if nothing else, such preprocessing (splitting variables into > core and peripherial groups) can make life easier in other > parts of the thing.
You're almost right. If you counted only explicit constraints, created by require statements, you get a bunch of cliques that aren't that large.
Unfortunately....there are a huge bunch of implicit constraints created by dependency relationships in the menu tree. For example, all SCSI cards are dependents of the SCSI symbol. Set SCSI to N and all the card symbols get turned off; set any card symbol to Y or M and the value of SCSI goes to Y or M correspondingly.
So the way it actually works (I think; I've have to write code to do a topological analysis to be sure) out is that there's sort of a light dust of atoms (BSD quota is one of them) surrounding one huge gnarly menu-tree-shaped clique. -- <a href="http://www.tuxedo.org/~esr/">Eric S. Raymond</a>
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