v.net.flow
Computes the maximum flow between two sets of nodes in the network.
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] [--verbose] [--quiet] [--qq] [--ui]
Example:
v.net.flow input=name output=name cut=name
grass.script.run_command("v.net.flow", input, arc_layer="1", node_layer="2", output, cut, arc_column=None, arc_backward_column=None, node_column=None, source_cats=None, source_where=None, sink_cats=None, sink_where=None, overwrite=False, verbose=False, quiet=False, superquiet=False)
Example:
gs.run_command("v.net.flow", input="name", output="name", cut="name")
Parameters
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
--overwrite
Allow output files to overwrite existing files
--help
Print usage summary
--verbose
Verbose module output
--quiet
Quiet module output
--qq
Very quiet module output
--ui
Force launching GUI dialog
input : str, required
Name of input vector map
Or data source for direct OGR access
Used as: input, vector, name
arc_layer : str, optional
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.
Used as: input, layer
Default: 1
node_layer : str, optional
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.
Used as: input, layer
Default: 2
output : str, required
Name for output vector map
Used as: output, vector, name
cut : str, required
Name for output vector map containing a minimum cut
Used as: output, vector, name
arc_column : str, optional
Arc forward/both direction(s) cost column (number)
Used as: input, dbcolumn, name
arc_backward_column : str, optional
Arc backward direction cost column (number)
Used as: input, dbcolumn, name
node_column : str, optional
Node cost column (number)
Used as: input, dbcolumn, name
source_cats : str, optional
Source category values
Example: 1,3,7-9,13
Used as: input, cats, range
source_where : str, optional
Source WHERE conditions of SQL statement without 'where' keyword
Example: income < 1000 and population >= 10000
Used as: input, sql_query, sql_query
sink_cats : str, optional
Sink category values
Example: 1,3,7-9,13
Used as: input, cats, range
sink_where : str, optional
Sink WHERE conditions of SQL statement without 'where' keyword
Example: income < 1000 and population >= 10000
Used as: input, sql_query, sql_query
overwrite: bool, optional
Allow output files to overwrite existing files
Default: False
verbose: bool, optional
Verbose module output
Default: False
quiet: bool, optional
Quiet module output
Default: False
superquiet: bool, optional
Very quiet module output
Default: False
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 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.
EXAMPLES
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
SEE ALSO
AUTHORS
Daniel Bundala, Google Summer of Code 2009, Student
Wolf Bergenheim, Mentor
SOURCE CODE
Available at: v.net.flow source code
(history)
Latest change: Friday Feb 07 19:16:09 2025 in commit a82a39f