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possible_path(+DistanceArg, +SourceNode, +SinkNode, +Tolerance, +Lengths, +Predecessors, -Path)

Computes an actual path from a predecessors array
DistanceArg
which argument of EdgeData to use as distance (integer)
SourceNode
source node number
SinkNode
sink node number
Tolerance
tolerable deviation from minimal length (non-negative number)
Lengths
array of numbers
Predecessors
array of edge lists
Path
Length-EdgeList structure

Description

This predicate complements the all_short_paths_as_edges/6 predicate. The intended usage is that all_short_paths_as_edges/6 is used to precompute shortest path information from a single source node to all possible sink nodes, and possible_path/7 uses this information to enumerate actual paths to a specific sink node. If paths from one source to several sinks are needed, it is more efficient to use one call to all_short_paths_as_edges/6 and several calls to possible_path/7, than to use several calls to single_pair_all_short_paths/7.

Note that the Lengths and Predecessors arrays must have been computed with the same settings for DistanceArg, SourceNode and Tolerance that are given to possible_path/7, otherwise errors or missing paths will occur.

Modes and Determinism

Fail Conditions

There is no path to SinkNode

Examples

    single_pair_shortest_path(Graph, Source, Sink, Path) :-
    	all_short_paths_as_edges(Graph, 0, Source, 0, Lengths, Preds),
    	possible_path(0, Source, Sink, 0, Lengths, Preds, Path).
    

See Also

all_short_paths_as_edges / 6