NAME¶
v.net.flow - Computes the maximum flow between two sets of nodes
in the network.
KEYWORDS¶
vector, network, flow
SYNOPSIS¶
v.net.flow
v.net.flow help
v.net.flow input=
name [
layer=
integer]
output=
name cut=
name [
afcolumn=
name]
[
abcolumn=
name] [
source_layer=
integer]
[
source_cats=
range] [
source_where=
sql_query]
[
sink_layer=
integer] [
sink_cats=
range]
[
sink_where=
sql_query] [--
overwrite] [--
verbose]
[--
quiet]
Flags:¶
- --overwrite
-
Allow output files to overwrite existing files
- --verbose
-
Verbose module output
- --quiet
-
Quiet module output
Parameters:¶
- input=name
-
Name of input vector map
- layer=integer
-
Layer number
A single vector map can be connected to multiple database tables. This
number determines which table to use.
Default: 1
- output=name
-
Name for output vector map
- cut=name
-
Name for output vector map containing a minimum cut
- afcolumn=name
-
Name of arc forward/both direction(s) capacity column
- abcolumn=name
-
Name of arc backward direction capacity column
- source_layer=integer
-
Source layer number or name
A single vector map can be connected to multiple database tables. This
number determines which table to use.
Default: 1
- source_cats=range
-
Source category values
Example: 1,3,7-9,13
- source_where=sql_query
-
Source WHERE conditions of SQL statement without 'where' keyword
Example: income = 10000
- sink_layer=integer
-
Sink layer number or name
A single vector map can be connected to multiple database tables. This
number determines which table to use.
Default: 1
- sink_cats=range
-
Sink category values
Example: 1,3,7-9,13
- sink_where=sql_query
-
Sink WHERE conditions of SQL statement without 'where' keyword
Example: income = 10000
DESCRIPTION¶
v.net.flow computes the maximum flow and minimum cut between two sets of
nodes.
NOTES¶
The two sets of nodes are called
sources and
sink and
v.net.flow finds the maximimum flow from the former to the latter ones.
Edge capacities can be specified by
afcolumn for forward direction and
abcolumn for backward direction. If the latter parameter is ommited
then the same capacity is used in either direction. The sets are given by the
respective
cats,
layer and
where parameters. Maximum flow
corresponds to the maximum amount of water possibly flowing through the
network preserving the capacity constraints and minimum cut to set of edges of
minimum total capacity completely separating sources from sinks. The cut
produced by this module corresponds to the first fully saturated edges from
sources to sinks. An attribute table containing the flow information is linked
to the
output map. The table consists of two columns:
cat and
flow and stores the flow along each line. Negative flow means that
"water" is flowing in the backward direction.
Cut map
contains the edges in the minimum cut.
A famous result says that the total amount of water flowing is equal to the
minimum cut.
EXAMPLES¶
Find maximum flow from factories to stores using SPEED for the capacities.
v.net.flow input=roads output=roads_flow cut=roads_cut afcolumn=SPEED
source_where="type=factory" sink_where="type=store"
If all the capacties are one then the minimum cut corresponds to the minimum
number of edges separating sources from sinks.
v.net.flow input=network output=flow cut=cut afcolumn=ones source_cats=1-10
sink_cats=100-100
SEE ALSO¶
v.net.connectivity
AUTHORS¶
Daniel Bundala, Google Summer of Code 2009, Student
Wolf Bergenheim, Mentor
Last changed: $Date: 2011-11-08 10:42:51 +0100 (Tue, 08 Nov 2011) $
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