Ankara : The Department of Computer Engineering and the Institute of Engineering and Science of Bilkent University, 2012.Thesis (Master's) -- Bilkent University, 2012.Includes bibliographical references leaves 72-74.Interactive graph editing plays an important role in information visualization
systems. For qualified analysis of the given data, an automated layout calculation
is needed. There have been numerous results published about automatic layout of
simple graphs, where the vertices are depicted as points in a 2D or 3D plane and
edges as straight lines connecting those points. But simple graphs are insufficient
to cover most real life information. Relational information is often clustered
or hierarchically organized into groups or nested structures. Compound spring
embedder (CoSE) of Chisio project is a layout algorithm based on a force-directed
layout scheme for undirected, non-uniform node sized compound graphs.
In order to satisfy the end-user, layout calculation process has to finish fast,
and the resulting layout should be eye pleasing. Therefore, several methods
were developed for improving both running time and the visual quality of the
layout. With the purpose of improving the visual quality of CoSE, we adapted
a multi-level scaling strategy. For improving the performance of the CoSE, the
grid-variant algorithm proposed by Fruchterman and Reingold and parallel force
calculation strategy by using graphics processing unit (GPU) were also adopted.
Additionally, tuning of the parameters like spring constant and cooling factor
were considered, as they affect the behavior of the physical system dramatically.
Our experiments show that after some tuning and adaptation of the methods
above, running time decreased and the visual quality of the layout improved
significantly.Karaçelik, AlperM.S