Previously graph layout was done using the Kamada-Kawai layout algorithm

implemented in Boost.  I am replacing this with a custom implementation of
a constrained stress-majorization algorithm.

The stress-majorization algorithm is more robust and has better convergence
characteristics than Kamada-Kawai, and also simple constraints can be placed
on node position (for example, to enforce downward-pointing edges, non-overlap constraints, or cluster constraints).

Another big advantage is that we no longer need Boost.

I've tested the basic functionality, but I have yet to properly handle
disconnected graphs or to properly scale the resulting layout.

This commit also includes significant refactoring... the quadratic program solver - libvpsc (Variable Placement with Separation Constraints) has been moved to src/libvpsc and the actual graph layout algorithm is in libcola.

(bzr r1394)

1 files changed, 51 insertions, 0 deletions

diff --git a/src/libvpsc/variable.h b/src/libvpsc/variable.h
new file mode 100644
index 000000000..b1ab66c95
--- /dev/null
+++ b/src/libvpsc/variable.h
@@ -0,0 +1,51 @@
+/**
+ *
+ * Authors:
+ *   Tim Dwyer <tgdwyer@gmail.com>
+ *
+ * Copyright (C) 2005 Authors
+ *
+ * Released under GNU LGPL.  Read the file 'COPYING' for more information.
+ */
+#ifndef SEEN_REMOVEOVERLAP_VARIABLE_H
+#define SEEN_REMOVEOVERLAP_VARIABLE_H
+
+#include <vector>
+#include <iostream>
+class Block;
+class Constraint;
+#include "block.h"
+
+typedef std::vector<Constraint*> Constraints;
+class Variable
+{
+	friend std::ostream& operator <<(std::ostream &os, const Variable &v);
+public:
+	const int id; // useful in log files
+	double desiredPosition;
+	const double weight;
+	double offset;
+	Block *block;
+	bool visited;
+	Constraints in;
+	Constraints out;
+	char *toString();
+	inline Variable(const int id, const double desiredPos, const double weight)
+		: id(id)
+		, desiredPosition(desiredPos)
+		, weight(weight)
+		, offset(0)
+		, block(NULL)
+		, visited(false)
+	{
+	}
+	inline double position() const {
+		return block->posn+offset;
+	}
+	//double position() const;
+	~Variable(void){
+		in.clear();
+		out.clear();
+	}
+};
+#endif // SEEN_REMOVEOVERLAP_VARIABLE_H