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Re: generation of random multiset permutation with restrictions
Posted:
Aug 21, 2012 4:16 AM
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"Michal Kvasnicka" wrote in message <k02f48$vs$1@newscl01ah.mathworks.com>...
> "Bruno Luong" <b.luong@fogale.findmycountry> wrote in message <k02c51$lo6$1@newscl01ah.mathworks.com>...
> > "Michal Kvasnicka" wrote in message <k006h5$9e6$1@newscl01ah.mathworks.com>...
> > > I am looking for MATLAB algorithm how to effectively generate any random multiset permutations with additional restrictions.
> > >
> > > Example: I have a multiset of items, for example: {1,1,1,2,2,3,3,3}, and a restricting set of sets, for example {{3},{1,2},{1,2,3},{1,2,3},{1,2,3},{1,2,3},{2,3},{2,3}. So, I am looking for permutations of items, but the first element must be 3, and the second must be 1 or 2, etc.
> > >
> > > One such permutation that fits the restrictions is: {3,1,1,1,2,2,3,3}
> > >
> > > Of course, any check if the restrictions are consistent, i.g. exist at least one possible permutation will important too.
> >
> > You might use Hungarian's assignment, one of such implementation is on FEX
> > http://www.mathworks.com/matlabcentral/fileexchange/6543
> >
> > a = [1,1,1,2,2,3,3,3]
> > s = {[3],[1,2],[1,2,3],[1,2,3],[1,2,3],[1,2,3],[2,3],[2,3]};
> >
> > % Engine
> > % Shuffle
> > p = a(randperm(length(a)));
> > % Distance matrix
> > D = cellfun(@(x) min(abs(bsxfun(@minus,x(:),p)),[],1), s, 'unif', 0);
> > D = cat(1,D{:});
> > [i cost] = assignmentoptimal(D);
> > if all(i) && cost==0
> > p = p(i');
> > disp(p)
> > else
> > disp('No solution');
> > end
> >
> > % Bruno
>
> Bruno, thank you very much for your help!!! The Hungarian's assignment perfectly solve may problem.
>
> Thanks again!
Bruno, could you help me once again? I need to perform so called "consistency" check, which mean, that I need to perform check if the current permutation satisfy the predefined restrictions.
Example:
a = [1,1,1,2,2,3,3,3]
s = {[3],[1,2],[1,2,3],[1,2,3],[1,2,3],[1,2,3],[2,3],[2,3]};
p1 = {3,1,1,1,2,2,3,3} -> OK
p2 = {1,3,1,1,2,2,3,3} -> not OK
Is there any simple way hot to use effectivelly Hungarian's assignment, too?
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