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..
****************************************************************************
pgRouting Manual
Copyright(c) pgRouting Contributors
This documentation is licensed under a Creative Commons Attribution-Share
Alike 3.0 License: https://creativecommons.org/licenses/by-sa/3.0/
****************************************************************************
|
* **Supported versions:**
`Latest <https://docs.pgrouting.org/latest/en/pgr_depthFirstSearch.html>`__
(`3.4 <https://docs.pgrouting.org/3.4/en/pgr_depthFirstSearch.html>`__)
`3.3 <https://docs.pgrouting.org/3.3/en/pgr_depthFirstSearch.html>`__
`3.2 <https://docs.pgrouting.org/3.2/en/pgr_depthFirstSearch.html>`__
``pgr_depthFirstSearch`` - Proposed
===============================================================================
``pgr_depthFirstSearch`` — Returns a depth first search traversal of the graph.
The graph can be directed or undirected.
.. figure:: images/boost-inside.jpeg
:target: https://www.boost.org/libs/graph/doc/depth_first_search.html
Boost Graph Inside
.. include:: proposed.rst
:start-after: stable-begin-warning
:end-before: stable-end-warning
.. rubric:: Availability
* Version 3.3.0
* Promoted to **proposed** function
* Version 3.2.0
* New **experimental** signatures:
* ``pgr_depthFirstSearch`` (`Single Vertex`_)
* ``pgr_depthFirstSearch`` (`Multiple Vertices`_)
Description
-------------------------------------------------------------------------------
Depth First Search algorithm is a traversal algorithm which starts from a root
vertex, goes as deep as possible, and backtracks once a vertex is reached with
no adjacent vertices or with all visited adjacent vertices. The traversal
continues until all the vertices reachable from the root vertex are visited.
**The main Characteristics are:**
- The implementation works for both **directed** and **undirected** graphs.
- Provides the Depth First Search traversal order from a root vertex or from a
set of root vertices.
- An optional non-negative maximum depth parameter to limit the results up to
a particular depth.
- For optimization purposes, any duplicated values in the `Root vids` are
ignored.
- It does not produce the shortest path from a root vertex to a target vertex.
- The aggregate cost of traversal is not guaranteed to be minimal.
- The returned values are ordered in ascending order of `start_vid`.
- Depth First Search Running time: :math:`O(E + V)`
Signatures
-------------------------------------------------------------------------------
.. rubric:: Summary
.. admonition:: \ \
:class: signatures
| pgr_depthFirstSearch(`Edges SQL`_, **root vid**, [**options**])
| pgr_depthFirstSearch(`Edges SQL`_, **root vids**, [**options**])
| **options:** ``[directed, max_depth]``
| RETURNS SET OF |result-bfs|
.. index::
single: depthFirstSearch(Single vertex) - Proposed on v3.3
Single vertex
...............................................................................
.. admonition:: \ \
:class: signatures
| pgr_depthFirstSearch(`Edges SQL`_, **root vid**, [**options**])
| **options:** ``[directed, max_depth]``
| RETURNS SET OF |result-bfs|
:Example: From root vertex :math:`6` on a **directed** graph with edges in
ascending order of ``id``
.. literalinclude:: doc-pgr_depthFirstSearch.queries
:start-after: -- q1
:end-before: -- q2
.. index::
single: depthFirstSearch(Multiple vertices) - Proposed on v3.3
Multiple vertices
...............................................................................
.. admonition:: \ \
:class: signatures
| pgr_depthFirstSearch(`Edges SQL`_, **root vids**, [**options**])
| **options:** ``[directed, max_depth]``
| RETURNS SET OF |result-bfs|
:Example: From root vertices :math:`\{12, 6\}` on an **undirected** graph with
**depth** :math:`<= 2` and edges in ascending order of ``id``
.. literalinclude:: doc-pgr_depthFirstSearch.queries
:start-after: -- q2
:end-before: -- q3
Parameters
-------------------------------------------------------------------------------
.. include:: BFS-category.rst
:start-after: mst-bfs-dfs-params_start
:end-before: mst-bfs-dfs-params_end
Optional parameters
...............................................................................
.. include:: dijkstra-family.rst
:start-after: dijkstra_optionals_start
:end-before: dijkstra_optionals_end
DFS optional parameters
...............................................................................
.. include:: BFS-category.rst
:start-after: max-depth-optional-start
:end-before: max-depth-optional-end
Inner Queries
-------------------------------------------------------------------------------
Edges SQL
...............................................................................
.. include:: pgRouting-concepts.rst
:start-after: basic_edges_sql_start
:end-before: basic_edges_sql_end
Return columns
-------------------------------------------------------------------------------
.. include:: BFS-category.rst
:start-after: mst-bfs-dfs-dd-result-columns-start
:end-before: mst-bfs-dfs-dd-result-columns-end
Additional Examples
-------------------------------------------------------------------------------
:Example: Same as `Single vertex`_ but with edges in descending order of ``id``.
.. literalinclude:: doc-pgr_depthFirstSearch.queries
:start-after: -- q3
:end-before: -- q4
The resulting traversal is different.
The left image shows the result with ascending order of ids and the right image
shows with descending order of the edge identifiers.
|ascending| |descending|
.. TODO fix the images
.. |ascending| image:: images/Fig1-AscendingOrder.png
:scale: 50%
.. |descending| image:: images/Fig2-DescendingOrder.png
:scale: 50%
See Also
-------------------------------------------------------------------------------
* :doc:`DFS-category`
* :doc:`sampledata`
* `Boost: Depth First Search algorithm documentation
<https://www.boost.org/libs/graph/doc/depth_first_search.html>`__
* `Boost: Undirected DFS algorithm documentation
<https://www.boost.org/libs/graph/doc/undirected_dfs.html>`__
* `Wikipedia: Depth First Search algorithm
<https://en.wikipedia.org/wiki/Depth-first_search>`__
.. rubric:: Indices and tables
* :ref:`genindex`
* :ref:`search`
|
