GSOC 2025: New function bandwidth to be added in pgRouting

[Saloni-2005]

pgr_bandwidth():

bandwidth(): The bandwidth of a graph is the maximum distance between two adjacent vertices, with distance measured on a line upon which the vertices have been placed at unit intervals. To put it another way, if the vertices of a graph G=(V,E) are each assigned an index from zero to |V| - 1 given by index[v], then the bandwidth of G is

B(G) = max { |index[u] - index[v]| | (u,v) in E }

Main characteristics of the function:

• Applicable for undirected graphs.
• Returns the bandwidth of the graph
• Run time is 0.160789 seconds

Signature:

• bandwidth()

bandwidth (Edges SQL)
RETURNS (bigint)
OR 0

Parameters:

Parameter	Type	Description
Edges SQL	TEXT	Inner SQL query, as described below.

Inner Query:

Edges SQL: It should be an SQL query which should return a BIGINT with the following columns:

Column	Type	Default	Description
id	ANY-INTEGER		Identifier of the edge
source	ANY-INTEGER		Identifier of the first end point vertex of the edge
target	ANY-INTEGER		Identifier of the second end point vertex of the edge
cost	ANY-NUMERICAL		Weight of the edge (source, target). When negative: edge (source, target) does not exist on the graph.
reverse_cost	ANY-NUMERICAL	-1	Weight of the edge (target, source). When negative: edge (target, source) does not exist on the graph.

Where:
ANY-INTEGER = SMALLINT, INTEGER, BIGINT
ANY-NUMERICAL = SMALLINT, INTEGER, BIGINT, REAL, FLOAT

Result Columns:

Returns (bigint)

Column	Type	Description
bandwidth	BIGINT	bandwidth of the graph