Jip J. Dekker
f2a1c4e389
git-subtree-dir: software/mza git-subtree-split: f970a59b177c13ca3dd8aaef8cc6681d83b7e813
33 lines
1.7 KiB
MiniZinc
33 lines
1.7 KiB
MiniZinc
include "tree.mzn";
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include "subgraph.mzn";
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predicate fzn_dpath(array[int] of $$N: from, array[int] of $$N: to,
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var $$N: s, var $$N: t, array[$$N] of var bool: ns, array[int] of var bool: es) =
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let { set of int: EDGE = index_set(es);
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array[index_set(ns)] of var 0..length(ns)-1: dist; /* distance from root */
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} in
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ns[s] /\ % source is selected
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ns[t] /\ % dest is selected
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dist[s] = 0 /\ % distance of source is zero
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forall(n in index_set(ns)) % nonselected nodes have distance 0
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(not ns[n] -> dist[n] = 0) /\
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forall(n in index_set(ns)) % 1 incoming edge
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((ns[n] /\ n != s) -> exists(e in EDGE where to[e] = n)(es[e])) /\
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forall(n in index_set(ns)) % 1 outgoing edge
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((ns[n] /\ n != t) -> exists(e in EDGE where from[e] = n)(es[e])) /\
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forall(n in index_set(ns)) % 1 incoming edge
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((ns[n] /\ n != s) -> sum(e in EDGE where to[e] = n)(es[e]) <= 1) /\
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forall(n in index_set(ns)) % 1 outgoing edge
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((ns[n] /\ n != t) -> sum(e in EDGE where from[e] = n)(es[e]) <= 1) /\
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% alternate for the previous 8 lines
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% forall(n in index_set(ns)) % 1 incoming edge
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% ((ns[n] /\ n != s) -> sum(e in EDGE where to[e] = n)(es[e]) = 1) /\
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% forall(n in index_set(ns)) % 1 outgoing edge
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% ((ns[n] /\ n != t) -> sum(e in EDGE where from[e] = n)(es[e]) = 1) /\
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forall(e in EDGE)
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(es[e] -> dist[to[e]] = dist[from[e]] + 1) /\
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sum(n in index_set(ns))(ns[n]) = sum(e in EDGE)(es[e]) + 1 /\
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subgraph(from,to,ns,es);
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%-----------------------------------------------------------------------------%
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