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

SOURCE CODE

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

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       © 2003-2019 GRASS Development Team, GRASS GIS 7.8.2 Reference Manual