v.net.flow - Computes the maximum flow between two sets of nodes
in the network.
vector, network, flow
v.net.flow
v.net.flow --help
v.net.flow input=
name [
arc_layer=
string]
[
node_layer=
string]
output=
name
cut=
name [
arc_column=
name]
[
arc_backward_column=
name] [
node_column=
name]
[
source_cats=
range] [
source_where=
sql_query]
[
sink_cats=
range] [
sink_where=
sql_query]
[--
overwrite] [--
help] [--
verbose] [--
quiet]
[--
ui]
- --overwrite
-
Allow output files to overwrite existing files
- --help
-
Print usage summary
- --verbose
-
Verbose module output
- --quiet
-
Quiet module output
- --ui
-
Force launching GUI dialog
- input=name [required]
-
Name of input vector map
Or data source for direct OGR access
- arc_layer=string
-
Arc layer
Vector features can have category values in different layers. This number
determines which layer to use. When used with direct OGR access this is
the layer name.
Default: 1
- node_layer=string
-
Node layer
Vector features can have category values in different layers. This number
determines which layer to use. When used with direct OGR access this is
the layer name.
Default: 2
- output=name [required]
-
Name for output vector map
- cut=name [required]
-
Name for output vector map containing a minimum cut
- arc_column=name
-
Arc forward/both direction(s) cost column (number)
- arc_backward_column=name
-
Arc backward direction cost column (number)
- node_column=name
-
Node cost column (number)
- 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 < 1000 and population >= 10000
- 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 < 1000 and population >= 10000
v.net.flow computes the maximum flow and minimum cut between two sets of
nodes.
The two sets of nodes are called
sources and
sink and
v.net.flow finds the maximum flow from the former to the latter ones.
Edge capacities can be specified by
arc_column for forward direction
and
arc_backward_column for backward direction. If the latter parameter
is omitted 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 the
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.
Find maximum flow from factories to stores using SPEED for the capacities.
v.net.flow input=roads output=roads_flow cut=roads_cut arc_column=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 arc_column=ones \
source_cats=1-10 sink_cats=100-100
v.net, v.net.connectivity
Daniel Bundala, Google Summer of Code 2009, Student
Wolf Bergenheim, Mentor
Last changed: $Date: 2016-08-30 15:28:34 +0200 (Tue, 30 Aug 2016) $
Available at: v.net.flow source code (history)
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