diff --git a/graph/src/main/scala/spark/graph/EdgeWithVerticesRDD.scala b/graph/src/main/scala/spark/graph/EdgeWithVerticesRDD.scala
index e787fe4e2c..f200f7cbf6 100644
--- a/graph/src/main/scala/spark/graph/EdgeWithVerticesRDD.scala
+++ b/graph/src/main/scala/spark/graph/EdgeWithVerticesRDD.scala
@@ -17,10 +17,10 @@ class EdgeWithVerticesPartition(idx: Int, val eTablePartition: Partition) extend
  * A RDD that brings together edge data with its associated vertex data.
  */
 private[graph]
-class EdgeWithVerticesRDD[VD: Manifest, ED: Manifest](
+class EdgeWithVerticesRDD[VD: ClassManifest, ED: ClassManifest](
     @transient vTable: RDD[(Vid, (VD, Array[Pid]))],
     eTable: RDD[(Pid, EdgePartition[ED])])
-  extends RDD[VertexHashMap, Iterator[EdgeWithVertices[VD, ED]]](eTable.context, Nil) {
+  extends RDD[(VertexHashMap[VD], Iterator[EdgeWithVertices[VD, ED]])](eTable.context, Nil) {
 
   @transient
   private val shuffleDependency = {
@@ -48,7 +48,7 @@ class EdgeWithVerticesRDD[VD: Manifest, ED: Manifest](
     eTable.preferredLocations(s.asInstanceOf[EdgeWithVerticesPartition].eTablePartition)
 
   override def compute(s: Partition, context: TaskContext)
-    : Iterator[VertexHashMap, Iterator[EdgeWithVertices[VD, ED]]] = {
+    : Iterator[(VertexHashMap[VD], Iterator[EdgeWithVertices[VD, ED]])] = {
 
     val split = s.asInstanceOf[EdgeWithVerticesPartition]
 
@@ -81,6 +81,6 @@ class EdgeWithVerticesRDD[VD: Manifest, ED: Manifest](
         e
       }
     }
-    (vmap, iter)
+    Iterator((vmap, iter))
   }
 }
diff --git a/graph/src/main/scala/spark/graph/Graph.scala b/graph/src/main/scala/spark/graph/Graph.scala
index 6e662ab1fb..5a1e06acdd 100644
--- a/graph/src/main/scala/spark/graph/Graph.scala
+++ b/graph/src/main/scala/spark/graph/Graph.scala
@@ -5,7 +5,8 @@ import scala.collection.mutable.ArrayBuffer
 
 import it.unimi.dsi.fastutil.ints.IntArrayList
 
-import spark.{ClosureCleaner, HashPartitioner, SparkContext, RDD}
+import spark.{ClosureCleaner, HashPartitioner, RDD}
+import spark.SparkContext
 import spark.SparkContext._
 import spark.graph.Graph.EdgePartition
 import spark.storage.StorageLevel
@@ -13,7 +14,10 @@ import spark.storage.StorageLevel
 
 case class Vertex[@specialized(Char, Int, Boolean, Byte, Long, Float, Double) VD] (
   var id: Vid = 0,
-  var data: VD = nullValue[VD])
+  var data: VD = nullValue[VD]) {
+
+  def this(tuple: Tuple2[Vid, VD]) = this(tuple._1, tuple._2)
+}
 
 
 case class Edge[@specialized(Char, Int, Boolean, Byte, Long, Float, Double) ED] (
@@ -37,37 +41,102 @@ class EdgeWithVertices[@specialized(Char, Int, Boolean, Byte, Long, Float, Doubl
 /**
  * A Graph RDD that supports computation on graphs.
  */
-class Graph[VD: Manifest, ED: Manifest](
-  val rawVertices: RDD[Vertex[VD]],
-  val rawEdges: RDD[Edge[ED]]) {
+class Graph[VD: ClassManifest, ED: ClassManifest] protected (
+  _rawVertices: RDD[Vertex[VD]],
+  _rawEdges: RDD[Edge[ED]],
+  _rawVTable: RDD[(Vid, (VD, Array[Pid]))],
+  _rawETable: RDD[(Pid, EdgePartition[ED])]) {
+
+  def this(vertices: RDD[Vertex[VD]], edges: RDD[Edge[ED]]) = this(vertices, edges, null, null)
+
+  protected var _cached = false
+
+  def cache(): Graph[VD, ED] = {
+    eTable.cache()
+    vTable.cache()
+    _cached = true
+    this
+  }
 
   var numEdgePartitions = 5
   var numVertexPartitions = 5
 
-  val vertexPartitioner = new HashPartitioner(numVertexPartitions)
+  protected val vertexPartitioner = new HashPartitioner(numVertexPartitions)
 
-  val edgePartitioner = new HashPartitioner(numEdgePartitions)
+  protected val edgePartitioner = new HashPartitioner(numEdgePartitions)
 
-  lazy val eTable: RDD[(Pid, EdgePartition[ED])] = Graph.createETable(
-    rawEdges, numEdgePartitions)
+  protected lazy val eTable: RDD[(Pid, EdgePartition[ED])] = {
+    if (_rawETable == null) {
+      Graph.createETable(_rawEdges, numEdgePartitions)
+    } else {
+      _rawETable
+    }
+  }
 
-  lazy val vTable: RDD[(Vid, (VD, Array[Pid]))] = Graph.createVTable(
-    rawVertices, eTable, numVertexPartitions)
+  protected lazy val vTable: RDD[(Vid, (VD, Array[Pid]))] = {
+    if (_rawVTable == null) {
+      Graph.createVTable(_rawVertices, eTable, numVertexPartitions)
+    } else {
+      _rawVTable
+    }
+  }
 
-  def vertices(): RDD[Vertex[VD]] = vTable.map { case(vid, (data, pids)) => new Vertex(vid, data) }
+  def vertices: RDD[Vertex[VD]] = {
+    if (!_cached && _rawVertices != null) {
+      _rawVertices
+    } else {
+      vTable.map { case(vid, (data, pids)) => new Vertex(vid, data) }
+    }
+  }
 
-  def edges(): RDD[Edge[ED]] = eTable.mapPartitions { iter => iter.next._2.iterator }
+  def edges: RDD[Edge[ED]] = {
+    if (!_cached && _rawEdges != null) {
+      _rawEdges
+    } else {
+      eTable.mapPartitions { iter => iter.next._2.iterator }
+    }
+  }
 
-  def edgesWithVertices(): RDD[EdgeWithVertices[VD, ED]] = {
-    (new EdgeWithVerticesRDD(vTable, eTable)).mapPartitions { case(vmap, iter) => iter }
+  def edgesWithVertices: RDD[EdgeWithVertices[VD, ED]] = {
+    (new EdgeWithVerticesRDD[VD, ED](vTable, eTable)).mapPartitions { part => part.next._2 }
+  }
+
+  def mapVertices[VD2: ClassManifest](f: (Vertex[VD]) => Vertex[VD2]) = {
+    ClosureCleaner.clean(f)
+    new Graph(vertices.map(f), edges)
+  }
+
+  def mapEdges[ED2: ClassManifest](f: (Edge[ED]) => Edge[ED2]) = {
+    ClosureCleaner.clean(f)
+    new Graph(vertices, edges.map(f))
+  }
+
+  def updateVertices[U: ClassManifest](
+      updates: RDD[(Vid, U)],
+      updateFunc: (Vertex[VD], Seq[U]) => VD)
+    : Graph[VD, ED] = {
+
+    ClosureCleaner.clean(updateFunc)
+
+    val joined: RDD[(Vid, ((VD, Array[Pid]), Option[Seq[U]]))] =
+      vTable.leftOuterJoin(updates.groupByKey(vertexPartitioner))
+
+    val newVTable = (joined.mapPartitions({ iter =>
+      iter.map { case (vid, ((vdata, pids), updates)) =>
+        val newVdata = if (updates.isDefined) updateFunc(Vertex(vid, vdata), updates.get) else vdata
+        (vid, (newVdata, pids))
+      }
+    }, preservesPartitioning = true)).cache()
+
+    new Graph(null, null, newVTable, eTable)
   }
 
   def mapPartitions[U: ClassManifest](
-    f: (VertexHashMap, Iterator[EdgeWithVertices[VD, ED]]) => Iterator[U],
+    f: (VertexHashMap[VD], Iterator[EdgeWithVertices[VD, ED]]) => Iterator[U],
     preservesPartitioning: Boolean = false): RDD[U] = {
     (new EdgeWithVerticesRDD(vTable, eTable)).mapPartitions({ part =>
        val (vmap, iter) = part.next()
-       iter.mapPartitions(f)
+       f(vmap, iter)
     }, preservesPartitioning)
   }
 
@@ -76,11 +145,48 @@ class Graph[VD: Manifest, ED: Manifest](
 
 object Graph {
 
+  /**
+   * Load an edge list from file initializing the Graph RDD
+   */
+  def textFile[ED: ClassManifest](sc: SparkContext,
+    fname: String, edgeParser: Array[String] => ED) = {
+
+    // Parse the edge data table
+    val edges = sc.textFile(fname).map { line =>
+      val lineArray = line.split("\\s+")
+      if(lineArray.length < 2) {
+        println("Invalid line: " + line)
+        assert(false)
+      }
+      val source = lineArray(0)
+      val target = lineArray(1)
+      val tail = lineArray.drop(2)
+      val edata = edgeParser(tail)
+      Edge(source.trim.toInt, target.trim.toInt, edata)
+    }.cache()
+
+    // Parse the vertex data table
+    val vertices = edges.flatMap { edge => List((edge.src, 1), (edge.dst, 1)) }
+      .reduceByKey(_ + _)
+      .map(new Vertex(_))
+
+    val graph = new Graph[Int, ED](vertices, edges)
+    graph.cache()
+
+    println("Loaded graph:" +
+      "\n\t#edges:    " + graph.edges.count +
+      "\n\t#vertices: " + graph.vertices.count)
+
+    graph
+  }
+
+
   /**
    * A partition of edges in 3 large columnar arrays.
    */
   private[graph]
-  class EdgePartition[@specialized(Char, Int, Boolean, Byte, Long, Float, Double) ED: Manifest] {
+  class EdgePartition[@specialized(Char, Int, Boolean, Byte, Long, Float, Double) ED:ClassManifest]
+  {
     val srcIds: IntArrayList = new IntArrayList
     val dstIds: IntArrayList = new IntArrayList
     // TODO: Specialize data.
@@ -104,7 +210,7 @@ object Graph {
       private var edge = new Edge[ED]
       private var pos = 0
 
-      override def hasNext: Boolean = pos < size
+      override def hasNext: Boolean = pos < EdgePartition.this.size
 
       override def next(): Edge[ED] = {
         edge.src = srcIds.get(pos)
@@ -117,7 +223,7 @@ object Graph {
   }
 
   private[graph]
-  def createVTable[VD: Manifest, ED: Manifest](
+  def createVTable[VD: ClassManifest, ED: ClassManifest](
       vertices: RDD[Vertex[VD]],
       eTable: RDD[(Pid, EdgePartition[ED])],
       numPartitions: Int) = {
@@ -145,7 +251,6 @@ object Graph {
         case (vdata, None)       => (vdata, Array.empty[Pid])
         case (vdata, Some(pids)) => (vdata, pids.toArray)
       }
-      .cache()
   }
 
   /**
@@ -157,7 +262,7 @@ object Graph {
    * containing all the edges in a partition.
    */
   private[graph]
-  def createETable[ED: Manifest](edges: RDD[Edge[ED]], numPartitions: Int)
+  def createETable[ED: ClassManifest](edges: RDD[Edge[ED]], numPartitions: Int)
   : RDD[(Pid, EdgePartition[ED])] = {
 
     edges.map { e =>
@@ -170,7 +275,6 @@ object Graph {
       iter.foreach { case (_, (src, dst, data)) => edgePartition.add(src, dst, data) }
       Iterator((pid, edgePartition))
     }, preservesPartitioning = true)
-    .cache()
   }
 
   /**
diff --git a/graph/src/main/scala/spark/graph/GraphLab.scala b/graph/src/main/scala/spark/graph/GraphLab.scala
index d90fdc3369..ce5b3f6e19 100644
--- a/graph/src/main/scala/spark/graph/GraphLab.scala
+++ b/graph/src/main/scala/spark/graph/GraphLab.scala
@@ -1,45 +1,57 @@
 package spark.graph
 
+import scala.collection.JavaConversions._
+import spark.RDD
+
 
 object GraphLab {
 
-  def iterateGAS[A: Manifest, VD: Manifest, ED: Manifest](
+  def iterateGAS[A: ClassManifest, VD: ClassManifest, ED: ClassManifest](
     graph: Graph[VD, ED],
     gather: (Vid, EdgeWithVertices[VD, ED]) => A,
     merge: (A, A) => A,
     default: A,
     apply: (Vertex[VD], A) => VD,
     numIter: Int,
-    gatherEdges: EdgeDirection = EdgeDirection.In) = {
+    gatherEdges: EdgeDirection.EdgeDirection = EdgeDirection.In) = {
 
-    val g = new Graph[(VD, A), ED](graph.rawVertices.map(v => (v, default)), graph.rawEdges)
+    var g = graph.mapVertices(v => Vertex(v.id, VDataWithAcc(v.data, default))).cache()
 
     var i = 0
     while (i < numIter) {
 
-      val gatherTable = g.mapPartitions { case(vmap, iter) =>
+      val accUpdates: RDD[(Vid, A)] = g.mapPartitions({ case(vmap, iter) =>
         val edgeSansAcc = new EdgeWithVertices[VD, ED]()
-        iter.map { edge: EdgeWithVertices[(VD, A), ED] =>
+        iter.map { edge: EdgeWithVertices[VDataWithAcc[VD, A], ED] =>
           edgeSansAcc.data = edge.data
-          edgeSansAcc.src.data = edge.src.data._1
-          edgeSansAcc.dst.data = edge.dst.data._1
+          edgeSansAcc.src.data = edge.src.data.vdata
+          edgeSansAcc.dst.data = edge.dst.data.vdata
           edgeSansAcc.src.id = edge.src.id
           edgeSansAcc.dst.id = edge.dst.id
           if (gatherEdges == EdgeDirection.In || gatherEdges == EdgeDirection.Both) {
-            edge.dst.data._2 = merge(edge.dst.data._2, gather(edgeSansAcc.dst.id, edgeSansAcc))
+            edge.dst.data.acc = merge(edge.dst.data.acc, gather(edgeSansAcc.dst.id, edgeSansAcc))
           }
           if (gatherEdges == EdgeDirection.Out || gatherEdges == EdgeDirection.Both) {
-            edge.src.data._2 = merge(edge.src.data._2, gather(edgeSansAcc.src.id, edgeSansAcc))
+            edge.src.data.acc = merge(edge.src.data.acc, gather(edgeSansAcc.src.id, edgeSansAcc))
           }
         }
 
-        vmap.int2ObjectEntrySet().fastIterator().map{ case (vid, (vdata, acc)) => (vid, acc) }
-      }.reduceByKey(graph.vertexPartitioner, false)
+        vmap.int2ObjectEntrySet().fastIterator().map{ entry =>
+          (entry.getIntKey(), entry.getValue().acc)
+        }
+      })(classManifest[(Int, A)])
 
-      gatherTable
+      def applyFunc(v: Vertex[VDataWithAcc[VD, A]], updates: Seq[A]): VDataWithAcc[VD, A] = {
+        VDataWithAcc(apply(Vertex(v.id, v.data.vdata), updates.reduce(merge)), default)
+      }
+      g = g.updateVertices(accUpdates, applyFunc).cache()
 
       i += 1
     }
   }
 
 }
+
+
+private[graph]
+sealed case class VDataWithAcc[VD: ClassManifest, A](var vdata: VD, var acc: A)
diff --git a/graph/src/main/scala/spark/graph/package.scala b/graph/src/main/scala/spark/graph/package.scala
index e900a27b27..6db050e6e1 100644
--- a/graph/src/main/scala/spark/graph/package.scala
+++ b/graph/src/main/scala/spark/graph/package.scala
@@ -4,8 +4,8 @@ package object graph {
 
   type Vid = Int
   type Pid = Int
-  type Status = Boolean
-  type VertexHashMap = it.unimi.dsi.fastutil.ints.Int2ObjectOpenHashMap
+
+  type VertexHashMap[T] = it.unimi.dsi.fastutil.ints.Int2ObjectOpenHashMap[T]
 
   /**
    * Return the default null-like value for a data type T.