The ULEL algorithm

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This layout algorithm iteratively searches for a configuration of the graph where the length of the links is close to a user-defined or a default value.

Example of ULEL algorithm

In CSS

The following example of a specification in CSS uses the Uniform Length Edges Layout algorithm. Since the Uniform Length Edges Layout places nodes and reshapes the links, it is usually not necessary to specify an additional link layout in CSS. The specification in CSS can be loaded as a style file into an application that uses the IlvDiagrammer class (see Graph Layout in Rogue Wave® JViews Diagrammer).

SDM {
    GraphLayout : "true";
    LinkLayout  : "false";
}

GraphLayout {
  graphLayout               : "UniformLengthEdges";
  linkStyle                 : "STRAIGHT_LINE_STYLE";
  preferredLinksLength      : "30";
  respectNodeSizes          : "true";
  layoutMode : "FAST_MULTILEVEL_MODE";
}

It is possible to enable the link layout additionally, and in this case, the link layout determines the shape of the links.

In Java

The following code sample uses the IlvUniformLengthEdgesLayout class. This code sample shows how to perform a Uniform Length Edges Layout on a grapher directly without using a diagram component or any style sheet:

 ...
import ilog.views.*;
import ilog.views.graphlayout.*;
import ilog.views.graphlayout.uniformlengthedges.*;
 ...
IlvGrapher grapher = new IlvGrapher();
IlvManagerView view = new IlvManagerView(grapher);

 ... /*   Fill in the grapher with nodes and links here */

IlvUniformLengthEdgesLayout layout = new
                                        IlvUniformLengthEdgesLayout();
layout.attach(grapher);
try {
        IlvUniformLengthEdgesLayoutReport layoutReport =  
                layout.performLayout();

        int code = layoutReport.getCode();

        System.out.println("Layout completed (" +
          layoutReport.codeToString(code) + ")");
}
catch (IlvGraphLayoutException e) {
        System.err.println(e.getMessage());
}

Important

All explanations in the subsequent sections regarding the shape of the links in Uniform Length Edges Layout are valid only if the link layout is disabled.

Current section

Uniform Length Edges (ULEL)