/**
* Like {@link #edgeLength(Graph,String)} but use an existing edge as argument.
*
* @param edge
* @return The edge length or -1 if the nodes of the edge have no positions.
*/
public static double edgeLength(Edge edge) {
double xyz0[] = nodePosition(edge.getNode0());
double xyz1[] = nodePosition(edge.getNode1());
if (xyz0 == null || xyz1 == null) return -1;
xyz0[0] = xyz1[0] - xyz0[0];
xyz0[1] = xyz1[1] - xyz0[1];
xyz0[2] = xyz1[2] - xyz0[2];
return Math.sqrt(xyz0[0] * xyz0[0] + xyz0[1] * xyz0[1] + xyz0[2] * xyz0[2]);
}
/*
* (non-Javadoc)
*
* @see org.graphstream.algorithm.Algorithm#compute()
*/
@SuppressWarnings("unchecked")
public void compute() {
Node source = graph.getNode(this.source_id);
// Step 1: Initialize graph
for (Node n : graph) {
if (n == source) n.addAttribute(identifier + ".distance", 0.0);
else n.addAttribute(identifier + ".distance", Double.POSITIVE_INFINITY);
// n.addAttribute(identifier+".predecessors",(Object)null);
}
// Step 2: relax edges repeatedly
for (int i = 0; i < graph.getNodeCount(); i++) {
for (Edge e : graph.getEachEdge()) {
Node n0 = e.getNode0();
Node n1 = e.getNode1();
Double d0 = (Double) n0.getAttribute(identifier + ".distance");
Double d1 = (Double) n1.getAttribute(identifier + ".distance");
Double we = (Double) e.getAttribute(weightAttribute);
if (we == null)
throw new NumberFormatException(
"org.graphstream.algorithm.BellmanFord: Problem with attribute \""
+ weightAttribute
+ "\" on edge "
+ e);
if (d0 != null) {
if (d1 == null || d1 >= d0 + we) {
n1.addAttribute(identifier + ".distance", d0 + we);
ArrayList<Edge> predecessors =
(ArrayList<Edge>) n1.getAttribute(identifier + ".predecessors");
if (d1 != null && d1 == d0 + we) {
if (predecessors == null) {
predecessors = new ArrayList<Edge>();
}
} else {
predecessors = new ArrayList<Edge>();
}
if (!predecessors.contains(e)) {
predecessors.add(e);
}
n1.addAttribute(identifier + ".predecessors", predecessors);
}
}
}
}
// Step 3: check for negative-weight cycles
for (Edge e : graph.getEachEdge()) {
Node n0 = e.getNode0();
Node n1 = e.getNode1();
Double d0 = (Double) n0.getAttribute(identifier + ".distance");
Double d1 = (Double) n1.getAttribute(identifier + ".distance");
Double we = (Double) e.getAttribute(weightAttribute);
if (we == null) {
throw new NumberFormatException(
String.format(
"%s: Problem with attribute \"%s\" on edge \"%s\"",
BellmanFord.class.getName(), weightAttribute, e.getId()));
}
if (d1 > d0 + we) {
throw new NumberFormatException(
String.format(
"%s: Problem: negative weight, cycle detected on edge \"%s\"",
BellmanFord.class.getName(), e.getId()));
}
}
}
