v.net.flow(1grass) | GRASS GIS User's Manual | v.net.flow(1grass) |
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]
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
Available at: v.net.flow source code (history)
Accessed: Sunday Jan 22 07:37:06 2023
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