com.sun.electric.database.topology.SteinerTree Maven / Gradle / Ivy
/* -*- tab-width: 4 -*-
*
* Electric(tm) VLSI Design System
*
* File: SteinerTree.java
* Written by: Steven Rubin.
*
* Copyright (c) 2012, Oracle and/or its affiliates. All rights reserved.
*
* Electric(tm) is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 3 of the License, or
* (at your option) any later version.
*
* Electric(tm) is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with Electric(tm); see the file COPYING. If not, write to
* the Free Software Foundation, Inc., 59 Temple Place, Suite 330,
* Boston, Mass 02111-1307, USA.
*/
package com.sun.electric.database.topology;
import com.sun.electric.database.geometry.EPoint;
import java.util.ArrayList;
import java.util.List;
/**
* Class for constructing a Steiner Tree.
*/
public class SteinerTree
{
private List pairs;
/**
* Interface to define a point in the Steiner Tree that needs to be organized properly.
* The PortInst class implements this.
*/
public interface SteinerTreePort
{
public EPoint getCenter();
}
/**
* Class that defines a branch of the Steiner Tree, with two SteinerTreePort objects.
*/
public static class SteinerTreePortPair
{
private SteinerTreePort p1, p2;
public SteinerTreePortPair(SteinerTreePort p1, SteinerTreePort p2)
{
this.p1 = p1;
this.p2 = p2;
}
public SteinerTreePort getPort1() { return p1; }
public SteinerTreePort getPort2() { return p2; }
}
/**
* Constructor takes a list of
* @param portList a List of SteinerTreePort objects that are to be organized into a Steiner Tree.
*/
public SteinerTree(List portList)
{
// the final list of edges in the Steiner tree
pairs = new ArrayList();
if (portList.size() < 2) return;
// a list of points that are already in the tree (initially contains the first point, a random choice)
List seen = new ArrayList();
seen.add(portList.get(0));
// initial list of points to be added to the tree (excluding the first point)
List remaining = new ArrayList();
for(int i=1; i 0)
{
// find the closest to anything in the Steiner tree
double bestDist = Double.MAX_VALUE;
SteinerTreePort bestRem = null, bestSeen = null;
for(SteinerTreePort piRem : remaining)
{
for(SteinerTreePort piSeen : seen)
{
double dist = piRem.getCenter().distance(piSeen.getCenter());
if (dist < bestDist)
{
bestDist = dist;
bestRem = piRem;
bestSeen = piSeen;
}
}
}
if (bestRem != null)
{
SteinerTreePortPair pp = makeTreeBranch(bestRem, bestSeen);
pairs.add(pp);
remaining.remove(bestRem);
seen.add(bestRem);
}
}
}
/**
* Overridable method to create a SteinerTreePortPair from two SteinerTreePort objects.
* @param p1 the first SteinerTreePort.
* @param p2 the second SteinerTreePort.
* @return a SteinerTreePortPair that encapsulates this branch of the Steiner Tree.
*/
public SteinerTreePortPair makeTreeBranch(SteinerTreePort p1, SteinerTreePort p2)
{
return new SteinerTreePortPair(p1, p2);
}
/**
* Method to return the Steiner Tree.
* @return a List of SteinerTreePortPair objects that describes the Steiner Tree.
*/
public List getTreeBranches()
{
return pairs;
}
}