From: Oliver Scheickl <scheickl_at_googlemail.com>

Date: Mon, 12 Oct 2009 15:52:01 +0200

Date: Mon, 12 Oct 2009 15:52:01 +0200

Dear all, In my little program I get an "instantiation fault" error message when ic:labeling starts. Maybe you can help me out of that issue. My problem to solve is quite simple: Given a graph consisting of connected edges; some of the edges can form a path. I want to distribute weights for the edges such that a) the weight of each edge does not exceed a certain value and b) the sum of weights of all edges of a path does also not exceed a certain value. Here is the complete ECLiPSe program. The example consists of only one path with three edges. The maximum edge weight is 3, the maximum path weight is 10: ----------------------snip------------------------- :- lib(ic). :- local struct(edgeWeight(edge, weight)). % facts (one path consisting of three edges) path(f1, node1, node4). edge(s1, node1, node2). edge(s2, node2, node3). edge(s3, node3, node4). % the main goal to solve solve(EdgeWeights) :- % fetch all edges and construct list EdgeWeights, % one struct in list for each edge; the weight of % each edge is to be found in the intervall 1..3 findall(E, edge(E, _, _), Edges), (foreach(Edge, Edges), foreach(EdgeWeight, EdgeWeights) do EdgeWeight = edgeWeight{edge:Edge, weight:Weight}, Weight :: 1..3 ), % fetch all paths; for each path the sum of edge % weights must be smaller than 10 findall(P, path(P, _, _), Paths), (foreach(Path, Paths), param(EdgeWeights) do % fetch all edges of one path allEdges(Path, Edges), % sum up the weights weightSum(Edges, EdgeWeights, Sum), % the only constraint Sum #< 10 ), labeling(EdgeWeights) . % sum up the weight of some edges weightSum( Edges, % a list of Edges EdgeWeights, % list of EdgeWeights of all edges WeightSum) :- % the sum of all wrights of edges in Edges list (foreach(Edge, Edges), fromto(0, In, Out, WeightSum), param(EdgeWeights) do weight(Edge, EdgeWeights, Weight), Out is In + Weight ). % get the Weight of Edge from EdgeWeights weight(Edge, EdgeWeights, Weight) :- member(edgeWeight{edge:Edge, weight:Weight}, EdgeWeights). % get all edges of one path allEdges(Path, Edges) :- path(Path, From, To), edgePath(From, To, [], Edges). edgePath(Hop, Hop, _, []). edgePath(From, To, Contained, [First | Rest]) :- edge(First, From, X), not(member(X, Contained)), edgePath(X, To, [X | Contained], Rest). ----------------------snip------------------------- What do you think of that solution in general? What am I doing wrong to get that error? Thanks for your help. Best regards, Oliver.Received on Mon Oct 12 2009 - 13:52:14 CEST

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