Graph now has DataFlow solvers!

git-svn-id: https://svn.apache.org/repos/asf/jakarta/commons/sandbox/graph2/trunk@144628 13f79535-47bb-0310-9956-ffa450edef68

src/java/org/apache/commons/graph/algorithm/dataflow/DataFlowEquations.java

@@ -0,0 +1,17 @@
+package org.apache.commons.graph.algorithm.dataflow;
+
+import java.util.BitSet;
+
+import org.apache.commons.graph.*;
+
+public interface DataFlowEquations {
+    /**
+     * This method shows when a definition is defined.
+     */
+    public BitSet generates( Vertex vertex );
+
+    /**
+     * This method shows when a definition is killed (or overwritten.)
+     */
+    public BitSet kills( Vertex vertex );
+}

src/java/org/apache/commons/graph/algorithm/dataflow/DataFlowSolutions.java

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+package org.apache.commons.graph.algorithm.dataflow;
+
+import java.util.Map;
+import java.util.BitSet;
+import java.util.HashMap;
+import java.util.Iterator;
+
+import org.apache.commons.graph.*;
+import org.apache.commons.graph.exception.*;
+import org.apache.commons.graph.domain.basic.*;
+
+
+public class DataFlowSolutions
+{
+    private Map inValues = new HashMap(); // VERTEX X BITSET
+    private Map outValues = new HashMap();
+
+    public DataFlowSolutions( DirectedGraph graph,
+			      DataFlowEquations eq ) {
+	calculateDataFlow( graph, eq );
+    }
+
+    private void calculateDataFlow( DirectedGraph graph,
+				    DataFlowEquations eq ) {
+	Iterator vertices = graph.getVertices().iterator();
+	while (vertices.hasNext()) {
+	    Vertex v = (Vertex) vertices.next();
+	    inValues.put( v, new BitSet() );   // Initialize everything to 
+	    outValues.put( v, new BitSet() );  // empty
+	}
+
+	boolean isOK = true;
+	while (isOK) {
+	    vertices = graph.getVertices().iterator();
+	    isOK = false;
+	    while (vertices.hasNext()) {
+		Vertex v = (Vertex) vertices.next();
+
+		BitSet out = new BitSet();
+		out.or( (BitSet) inValues.get( v ));
+		out.or( eq.generates( v ));
+		out.andNot( eq.kills( v ));
+		
+		/*
+		System.err.println("Old Out: " + v + ":" + outValues.get( v ));
+		System.err.println("New Out: " + v + ":" + out);
+		*/
+		if (!out.equals( outValues.get( v ))) {
+		    isOK = true;
+		    outValues.put( v, out );
+
+		    Iterator outbound = graph.getOutbound( v ).iterator();
+		    while (outbound.hasNext()) {
+			Vertex target = 
+			    graph.getTarget( (Edge) outbound.next() );
+			
+			BitSet in = (BitSet) inValues.get( target );
+			in.or( out );
+			inValues.put( target, in );
+			/*
+			System.err.println("Old In: " + target + ":" + 
+					   inValues.get( target ));
+			System.err.println("New In: " + target + ":" + in );
+			*/
+		    }
+		}
+	    }
+	}
+    }
+
+    public BitSet reaches( Vertex vertex ) {
+	return (BitSet) inValues.get( vertex );
+    }
+
+    public BitSet leaves( Vertex vertex ) {
+	return (BitSet) outValues.get( vertex );
+    }
+}