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 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 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, v.net.connectivity

AUTHORS

       Daniel Bundala, Google Summer of Code 2009, Student
       Wolf Bergenheim, Mentor

       Last changed: $Date: 2013-05-23 13:01:55 -0700 (Thu, 23 May 2013) $

       Full index

       © 2003-2013 GRASS Development Team

GRASS 6.4.3                                                                                   v.net.flow(1grass)