pgr_bdAstarCostMatrix - proposed¶

Name¶

pgr_bdAstarCostMatrix - Calculates the a cost matrix using pgr_bdAstar.

Boost Graph Inside

Availability: 2.5.0

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 ANY-INTEGER and ANY-NUMERICAL
- 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

Synopsis¶

Using Dijkstra algorithm, calculate and return a cost matrix.

Signature Summary¶

pgr_bdAstarCostMatrix(edges_sql, start_vids)
pgr_bdAstarCostMatrix(edges_sql, start_vids, [, directed , heuristic, factor, epsilon])
RETURNS SET OF (start_vid, end_vid, agg_cost)
OR EMPTY SET

Signatures¶

Minimal Signature¶

pgr_bdAstarCostMatrix(edges_sql, start_vids)
RETURNS SET OF (start_vid, end_vid, agg_cost)
OR EMPTY SET

This usage calculates the cost from the each start_vid in start_vids to each start_vid in start_vids

on a directed graph
with heuristic’s value 5
with factor’s value 1
with epsilon’s value 1

Example:	Cost matrix for vertices 1, 2, 3, and 4.

SELECT * FROM pgr_bdAstarCostMatrix(
    'SELECT id, source, target, cost, reverse_cost, x1, y1, x2, y2 FROM edge_table',
    (SELECT array_agg(id) FROM edge_table_vertices_pgr WHERE id < 5)
);
 start_vid | end_vid | agg_cost 
-----------+---------+----------
         1 |       2 |        1
         1 |       3 |       12
         1 |       4 |       12
         2 |       1 |        1
         2 |       3 |       10
         2 |       4 |        9
         3 |       1 |        2
         3 |       2 |        1
         3 |       4 |        5
         4 |       1 |        5
         4 |       2 |        2
         4 |       3 |        1
(12 rows)

Complete Signature¶

pgr_bdAstarCostMatrix(edges_sql, start_vids, [, directed , heuristic, factor, epsilon])
RETURNS SET OF (start_vid, end_vid, agg_cost)
OR EMPTY SET

This usage calculates the cost from the each start_vid in start_vids to each start_vid in start_vids allowing the user to choose

if the graph is directed or undirected
heuristic,
and/or factor
and/or epsilon.

Example:	Cost matrix for an undirected graph for vertices 1, 2, 3, and 4.

This example returns a symmetric cost matrix.

SELECT * FROM pgr_bdAstarCostMatrix(
    'SELECT id, source, target, cost, reverse_cost, x1, y1, x2, y2 FROM edge_table',
    (SELECT array_agg(id) FROM edge_table_vertices_pgr WHERE id < 5),
    false
);
 start_vid | end_vid | agg_cost 
-----------+---------+----------
         1 |       2 |        1
         1 |       3 |        2
         1 |       4 |        5
         2 |       1 |        1
         2 |       3 |        1
         2 |       4 |        2
         3 |       1 |        2
         3 |       2 |        1
         3 |       4 |        1
         4 |       1 |        5
         4 |       2 |        2
         4 |       3 |        1
(12 rows)

Description of the Signatures¶

Description of the edges_sql query for astar like functions¶

edges_sql:	an SQL query, which should return a set of rows 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, therefore it’s not part of the graph.
reverse_cost	`ANY-NUMERICAL`	-1	Weight of the edge (target, source), When negative: edge (target, source) does not exist, therefore it’s not part of the graph.
x1	`ANY-NUMERICAL`		X coordinate of source vertex.
y1	`ANY-NUMERICAL`		Y coordinate of source vertex.
x2	`ANY-NUMERICAL`		X coordinate of target vertex.
y2	`ANY-NUMERICAL`		Y coordinate of target vertex.

Where:

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

Description of the parameters of the signatures¶

Parameter	Type	Description
edges_sql	`TEXT`	Edges SQL query as described above.
start_vid	`ANY-INTEGER`	Starting vertex identifier.
start_vids	`ARRAY[ANY-INTEGER]`	Starting vertices identifierers.
end_vid	`ANY-INTEGER`	Ending vertex identifier.
end_vids	`ARRAY[ANY-INTEGER]`	Ending vertices identifiers.
directed	`BOOLEAN`	Optional. When `false` the graph is considered as Undirected. Default is `true` which considers the graph as Directed.
heuristic	`INTEGER`	(optional). Heuristic number. Current valid values 0~5. Default `5` 0: h(v) = 0 (Use this value to compare with pgr_dijkstra) 1: h(v) abs(max(dx, dy)) 2: h(v) abs(min(dx, dy)) 3: h(v) = dx * dx + dy * dy 4: h(v) = sqrt(dx * dx + dy * dy) 5: h(v) = abs(dx) + abs(dy)
factor	`FLOAT`	(optional). For units manipulation. \(factor > 0\). Default `1`. see Factor
epsilon	`FLOAT`	(optional). For less restricted results. \(epsilon >= 1\). Default `1`.

Description of the return values for a Cost function¶

Returns set of (start_vid, end_vid, agg_cost)

Column	Type	Description
start_vid	`BIGINT`	Identifier of the starting vertex. Used when multiple starting vetrices are in the query.
end_vid	`BIGINT`	Identifier of the ending vertex. Used when multiple ending vertices are in the query.
agg_cost	`FLOAT`	Aggregate cost from `start_vid` to `end_vid`.

Examples¶

Example:	Use with tsp

SELECT * FROM pgr_TSP(
    $$
    SELECT * FROM pgr_bdAstarCostMatrix(
        'SELECT id, source, target, cost, reverse_cost, x1, y1, x2, y2 FROM edge_table',
        (SELECT array_agg(id) FROM edge_table_vertices_pgr WHERE id < 5),
        false
    )
    $$,
    randomize := false
);
 seq | node | cost | agg_cost 
-----+------+------+----------
   1 |    1 |    2 |        0
   2 |    3 |    1 |        2
   3 |    4 |    2 |        3
   4 |    2 |    1 |        5
   5 |    1 |    0 |        6
(5 rows)