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

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

• possible_path(+, +, +, +, +, +, -) is nondet

Fail Conditions

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