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   [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]

   Flags:
       --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

   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

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

        v.net, v.net.connectivity

AUTHORS

       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) $

SOURCE CODE

       Available at: v.net.flow source code (history)

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       © 2003-2018 GRASS Development Team, GRASS GIS 7.4.0 Reference Manual