Package ghidra.graph.algo

# Class DijkstraShortestPathsAlgorithm.OneSourceToAll

java.lang.Object
ghidra.graph.algo.DijkstraShortestPathsAlgorithm.OneSourceToAll

Enclosing class:
  DijkstraShortestPathsAlgorithm<V,E extends GEdge<V>>

protected class DijkstraShortestPathsAlgorithm.OneSourceToAll extends Object
A class representing all optimal paths from a given source to every other (reachable) vertex in the graph

This is the workhorse of path computation, and implements Dijkstra's Shortest Path algorithm from one source to all destinations. We considered using JUNG to store the graph and compute the paths, but we could not, because we would like to find all paths having the optimal distance. If there are ties, JUNG's implementation chooses one arbitrarily; we would like all tied paths.

- ## Field Summary

  Fields
  Modifier and Type
  Field
  Description
  `protected final Map<V,Set<E>>`
  `bestIns`
  `protected final ValueSortedMap<V,Double>`
  `queueByDistance`
  `protected final V`
  `source`
  `protected final Map<V,Double>`
  `visitedDistance`

- ## Constructor Summary

  Constructors
  Modifier
  Constructor
  Description
  `protected`
  `OneSourceToAll(V src)`
  Compute the shortest paths from a given vertex to all other reachable vertices in the graph

- ## Method Summary

  Modifier and Type
  Method
  Description
  `protected boolean`
  `addOrUpdate(V dest, double newDist)`
  Update the record for the given destination with a new offer of shortest distance
  `protected void`
  `addPathsTo(Collection<Deque<E>> paths, V dst)`
  Add the shortest paths from the source to the given destination into the given collection
  `protected void`
  `addPathsTo(Collection<Deque<E>> paths, V prev, Deque<E> soFar)`
  Add the shortest paths from source to a given intermediate, continuing along a given path to the final destination, into the given collection
  `Collection<Deque<E>>`
  `computeOptimalPathsTo(V dst)`
  Recover the shortest paths from the source to the given destination, if it is reachable
  `protected void`
  `fill()`
  Compute paths, building out the graph until all reachable vertices have been visited
  `protected void`
  `fillStep(V from, double dist)`
  Perform one iteration of Dijskstra's path finding algorithm

  ### Methods inherited from class java.lang.Object

  `clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

- ## Field Details

  - ### queueByDistance

    protected final ValueSortedMap<V,Double> queueByDistance

  - ### visitedDistance

    protected final Map<V,Double> visitedDistance

  - ### bestIns

    protected final Map<V,Set<E extends GEdge<V>>> bestIns

  - ### source

    protected final V source

- ## Constructor Details

  - ### OneSourceToAll

    protected OneSourceToAll(V src)
    Compute the shortest paths from a given vertex to all other reachable vertices in the graph
    Parameters:
      `src` - the source (seed) vertex

- ## Method Details

  - ### computeOptimalPathsTo

    public Collection<Deque<E>> computeOptimalPathsTo(V dst)
    Recover the shortest paths from the source to the given destination, if it is reachable
    Parameters:
      `dst` - the destination
    Returns:
      a collection of the shortest paths from source to destination, or the empty set

  - ### addPathsTo

    protected void addPathsTo(Collection<Deque<E>> paths, V dst)
    Add the shortest paths from the source to the given destination into the given collection

    This is used internally to recover the shortest paths

    Parameters:
      `paths` - a place to store the recovered paths
      `dst` - the destination

  - ### addPathsTo

    protected void addPathsTo(Collection<Deque<E>> paths, V prev, Deque<E> soFar)
    Add the shortest paths from source to a given intermediate, continuing along a given path to the final destination, into the given collection

    This is a recursive method for constructing the shortest paths overall. Assuming the given path from intermediate to final destination is the shortest, we can show by induction, the computed paths from source to destination are the shortest.

    Parameters:
      `paths` - a place to store the recovered paths
      `prev` - the intermediate destination
      `soFar` - a (shortest) path from intermediate to final destination

  - ### addOrUpdate

    protected boolean addOrUpdate(V dest, double newDist)
    Update the record for the given destination with a new offer of shortest distance

    If either the record doesn't exist yet, or the new offer beats the current best, then a new record is created and replaces the current record. If present, the list of best inbound edges is cleared -- because they all correspond to a distance that has just been beat. The node is also added and/or moved forward in the queue of unvisited vertices.

    If the record exists, and the new offer ties the current offer, nothing happens, but the method still returns true, since the corresponding inbound edge could be optimal.

    If the record's current best beats the offer, nothing happens, and the method returns false, indicating the inbound edge is definitely not optimal.

    Parameters:
      `dest` - the destination whose record to update
      `newDist` - the distance offer
    Returns:
      true iff the offer is equal to or better than the record's current best

  - ### fill

    protected void fill()
    Compute paths, building out the graph until all reachable vertices have been visited

  - ### fillStep

    protected void fillStep(V from, double dist)
    Perform one iteration of Dijskstra's path finding algorithm
    Parameters:
      `from` - the vertex to visit for this iteration