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T E L E C O M M U N I C A T I O N S TELECOMMUNICATIONS: Excerpt of User List
By using LEDA's graph and graph
related data types you can easily model your network in a natural way. Nodes and
edges can be parameterized with arbitrary values.
Why LEDA : Beyond the data type graph itself
LEDA offers many different types and methods to associate data
to the network elements. The standard graph type is fully dynamic
and allows a great variety of modifications. There is
also a family of semi-static and static graph types available offering
better time and space performance than any other implementation
on the world.
Optimizing Capacities, Costs And Traffic. To minimize the costs of your network you have to optimize its entire performance: capacities, traffic, and space. Why LEDA : In
LEDA you find ready-to-use shortest path algorithms, min
cost flow algorithms, matchings and assignments, minimum
spanning trees, etc., altogether more than 200 pre-built
methods that can easily be plugged into
your applications. Many of the algorithms prove
their results by short and understandable test routines relying
on mathematical theorems. In addition you can easily extend
LEDA's functionality by building your own algorithms on top
of LEDA's data types and methods.
Visualize And Manage Your Network Use the available grafical user interface and visualization capabilities of LEDA to view and interactively modify your communication network.
Improve Runtimes On Large Networks To improve running times is easy - simply use LEDA's static graph feature and improve space requirements by up to 60 and running times by up to 70 percent! SPECIAL FEATURE: Static Graphs What are Static Graphs? Most graph algorithms do not change the underlying graph. Rather, they work on a constant or static graph. A static graph consists of a fixed sequence of nodes and edges. New nodes or edges can be appended only in a construction phase which has to be started by calling G.start_construction() and terminated by G.finish_construction(). After the construction phase both sequences V and E are fixed.
There are different models of static graphs; the class is parameterized by the so called graph category. There are directed graphs, bidirectional graphs, opposite graphs, bidirected graphs and undirected graphs. Currently, the first three are available. Finally, static graphs support several efficient ways - efficient compared to using node_arrays, edge_arrays, node_maps, and edge_maps - to associate data with the edges and nodes of the graph. The manual page explains the details. Why should you use Static Graphs? In many cases static graphs are much more efficient (time as well as space efficient) than other graph implementations. In our experiments, running maxflow algorithms on networks produced by the ak-generator of Cherkassy and Goldberg, we received the following results: The runtime improvement is up
to 65% (or even up to 75% if we compare static graphs
using static slots with LEDA 5.1 brings new implementations, the time efficiency of several flow algorithms improved even more. Note:
It can even make sense
to transform a fully dynamic graph to a fully static graph
before running an optimization algorithm on it. The time
loss for the transformation usually is easily compensated
by the better running times of the algorithm on the static
graph representation.
Samples: Documentation:
EXAMPLE APPLICATION: Mobile Connect Radio Tracer RadioTracer is a simulation program which estimates the electromagnetic characteristics of wireless and mobile telecommunication systems. Accurate prediction of the mobile channel is an important issue when planning modern wireless systems. RadioTracer implements the deterministic approach based on the uniform theory of diffraction in a very efficient way such that even complex simulations can be executed in a reasonable amount of time. LEDA's basic data structures are used for maintaining
and storing data, the graph data type stores the radio paths. The
visualization of the different computations and diagrams is programmed
using
mobile connect GmbH, Germany: Radio Tracer The Framework for Implicit Graph Algorithms and Representations by OBDD (Ordered Binary Decision Diagram)s - The Figaro - is part of the project Algorithms on Implicit Networks (http://ls2-www.cs.uni-dortmund.de/spp1126) and concerned with efficient algorithms for problems on implicitly, in particular by OBDDs represented networks. These are heuristics for large and structured networks, where traditional algorithms cannot be applied. LEDA data structures are used for the representation and input/output of explicit (adjacency list based) graphs. Furthermore, LEDA's flow maximization and flow verification algorithms are used by plugins. In addition, LEDA's random generator and its basic data structures are used. University of Dortmund, Germany: FIGARO |
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