v.net.flow(1grass)
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 inhab >= 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 inhab >= 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 15:30:14 +0200 (Tue, 30 Aug 2016) $
SOURCE CODE
Available at: v.net.flow source code (history)
Main index | Vector index | Topics index | Keywords index | Graphical
index | Full index
2003-2016 GRASS Development Team, GRASS GIS 7.2.0 Reference Manual
Opportunity
Personal Opportunity - Free software gives you access to billions of dollars of software at no cost. Use this software for your business, personal use or to develop a profitable skill. Access to source code provides access to a level of capabilities/information that companies protect though copyrights. Open source is a core component of the Internet and it is available to you. Leverage the billions of dollars in resources and capabilities to build a career, establish a business or change the world. The potential is endless for those who understand the opportunity.
Business Opportunity - Goldman Sachs, IBM and countless large corporations are leveraging open source to reduce costs, develop products and increase their bottom lines. Learn what these companies know about open source and how open source can give you the advantage.
Free Software
Free Software provides computer programs and capabilities at no cost but more importantly, it provides the freedom to run, edit, contribute to, and share the software. The importance of free software is a matter of access, not price. Software at no cost is a benefit but ownership rights to the software and source code is far more significant.
Free Office Software - The Libre Office suite provides top desktop productivity tools for free. This includes, a word processor, spreadsheet, presentation engine, drawing and flowcharting, database and math applications. Libre Office is available for Linux or Windows.
Free Books
The Free Books Library is a collection of thousands of the most popular public domain books in an online readable format. The collection includes great classical literature and more recent works where the U.S. copyright has expired. These books are yours to read and use without restrictions.
Source Code - Want to change a program or know how it works? Open Source provides the source code for its programs so that anyone can use, modify or learn how to write those programs themselves. Visit the GNU source code repositories to download the source.
Education
Study at Harvard, Stanford or MIT - Open edX provides free online courses from Harvard, MIT, Columbia, UC Berkeley and other top Universities. Hundreds of courses for almost all major subjects and course levels. Open edx also offers some paid courses and selected certifications.
Linux Manual Pages - A man or manual page is a form of software documentation found on Linux/Unix operating systems. Topics covered include computer programs (including library and system calls), formal standards and conventions, and even abstract concepts.
