From 9ce65c5a963b03ee97fe9cb6c5aa65a3c04a80a8 Mon Sep 17 00:00:00 2001
From: yzhou <yujiao.zhou@gmail.com>
Date: Tue, 21 Apr 2015 10:34:27 +0100
Subject: initial version

---
 test/uk/ac/ox/cs/data/sample/RandomWalk.java | 88 ++++++++++++++++++++++++++++
 1 file changed, 88 insertions(+)
 create mode 100644 test/uk/ac/ox/cs/data/sample/RandomWalk.java

(limited to 'test/uk/ac/ox/cs/data/sample/RandomWalk.java')

diff --git a/test/uk/ac/ox/cs/data/sample/RandomWalk.java b/test/uk/ac/ox/cs/data/sample/RandomWalk.java
new file mode 100644
index 0000000..d9f5107
--- /dev/null
+++ b/test/uk/ac/ox/cs/data/sample/RandomWalk.java
@@ -0,0 +1,88 @@
+package uk.ac.ox.cs.data.sample;
+
+import java.util.HashSet;
+import java.util.Iterator;
+import java.util.List;
+import java.util.Random;
+import java.util.Set;
+import java.util.Stack;
+
+import org.openrdf.rio.RDFHandlerException;
+import org.openrdf.rio.turtle.TurtleWriter;
+
+import uk.ac.ox.cs.pagoda.util.Utility;
+
+public class RandomWalk extends Sampler {
+	
+	public RandomWalk(RDFGraph graph, TurtleWriter writer) {
+		super(graph, writer);
+	}
+
+	protected Random rand = new Random(); 
+	
+	protected int noOfStatements = 0, statementLimit = 0;
+	protected Set<Integer> visited = new HashSet<Integer>();
+	
+	@Override
+	public void setLimit(int limit) {
+		statementLimit = limit; 
+	}
+	
+	@Override
+	public void sample() throws RDFHandlerException {
+		int u, v, pick, index; 
+		RDFEdge edge; 
+		List<RDFEdge> edges;
+		Stack<Integer> stack = new Stack<Integer>();
+		while (true) {
+			if (noOfStatements >= statementLimit) {
+				return ; 
+			}
+			if (stack.isEmpty()) {
+				stack.add(v = rand.nextInt(m_graph.numberOfIndividuals));
+				Utility.logInfo("A new start: " + m_graph.getRawString(v));
+				visit(v);
+			}
+			u = stack.peek(); 
+			if (rand.nextInt(100) < 15) {
+				stack.pop(); 
+				continue;
+			}
+			if ((edges = m_graph.edges.get(u)) == null || edges.size() == 0) {
+				stack.clear();
+				continue; 
+			}
+			
+			index = 0;
+			pick = rand.nextInt(edges.size()); 
+			for (Iterator<RDFEdge> iter = edges.iterator(); iter.hasNext(); ++index) {
+				edge = iter.next(); 
+				if (index == pick) {
+					stack.add(v = edge.m_dst);
+					visit(v);
+					m_writer.handleStatement(m_graph.getStatement(u, edge.m_label, edge.m_dst));
+					++noOfStatements; 
+					iter.remove(); 
+				}
+					
+			}
+		}
+	}
+
+	protected void visit(int node) throws RDFHandlerException {
+		if (visited.contains(node)) return ; 
+		visited.add(node); 
+		List<Integer> list = m_graph.labels.get(node);
+		if (list == null) return ; 
+		for (Iterator<Integer> iter = list.iterator(); iter.hasNext(); )  
+			m_writer.handleStatement(m_graph.getStatement(node, iter.next()));
+		noOfStatements += list.size(); 
+	}
+
+	@Override
+	public void dispose() {
+		visited.clear();
+	}
+	
+	
+}
-- 
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