pgr_bipartite Experimental¶
pgr_bipartite
— If graph is bipartite then function returns the vertex id along with color (0 and 1) else it will return an empty set.
In particular, the is_bipartite() algorithm implemented by Boost.Graph.
Warning
Possible server crash
These functions might create a server crash
Warning
Experimental functions
They are not officially of the current release.
They likely will not be officially be part of the next release:
The functions might not make use of ANYINTEGER and ANYNUMERICAL
Name might change.
Signature might change.
Functionality might change.
pgTap tests might be missing.
Might need c/c++ coding.
May lack documentation.
Documentation if any might need to be rewritten.
Documentation examples might need to be automatically generated.
Might need a lot of feedback from the comunity.
Might depend on a proposed function of pgRouting
Might depend on a deprecated function of pgRouting
Availability
Version 3.2.0
New experimental function
Description¶
A bipartite graph is a graph with two sets of vertices which are connected to each other, but not within themselves. A bipartite graph is possible if the graph coloring is possible using two colors such that vertices in a set are colored with the same color.
The main Characteristics are:
The algorithm works in undirected graph only.
The returned values are not ordered.
The algorithm checks graph is bipartite or not. If it is bipartite then it returns the node along with two colors 0 and 1 which represents two different sets.
If graph is not bipartite then algorithm returns empty set.
Running time: \(O(V + E)\)
Signatures¶
pgr_bipartite(Edges SQL)  Experimental on v3.2
RETURNS SET OF (vertex_id, color_id)
OR EMPTY SET
 Example
The pgr_bipartite algorithm with and edge_sql as a parameter when graph is bipartite:
SELECT * FROM pgr_bipartite(
$$SELECT id,source,target,cost,reverse_cost FROM edge_table$$
);
vertex_id  color_id
+
1  0
2  1
3  0
4  1
5  0
6  1
7  0
8  1
9  0
10  1
11  0
12  1
13  0
14  0
15  1
16  0
17  1
(17 rows)
Parameters¶
Parameter 
Type 
Description 

Edges SQL 

Inner query as described below. 
Inner query¶
 Edges SQL
an SQL query of an undirected graph, which should return a set of rows with the following columns:
Column 
Type 
Default 
Description 

id 

Identifier of the edge. 

source 

Identifier of the first end point vertex of the edge. 

target 

Identifier of the second end point vertex of the edge. 

cost 



reverse_cost 

1 

Where:
 ANYINTEGER
SMALLINT, INTEGER, BIGINT
 ANYNUMERICAL
SMALLINT, INTEGER, BIGINT, REAL, FLOAT
Result Columns¶
Returns SET OF (vertex_id, color_id)
Column 
Type 
Description 

vertex_id 

Identifier of the vertex. 
color_id 

Identifier of the color of the vertex.

Additional Example¶
 Example
The odd length cyclic graph can not be bipartite.
The following edge will make subgraph with vertices {1, 2, 5, 7, 8} an odd length cyclic graph.
INSERT INTO edge_table (source, target, cost, reverse_cost) VALUES
(1, 7, 1, 1);
INSERT 0 1
The new graph is not bipartite because it has a odd length cycle of 5 vertices. Edges in blue represent odd length cycle.
SELECT * FROM pgr_bipartite(
$$SELECT id,source,target,cost,reverse_cost FROM edge_table$$
);
vertex_id  color_id
+
(0 rows)