Github user wickedshimmy commented on a diff in the pull request:
https://github.com/apache/spark/pull/1217#discussion_r15646928
--- Diff: graphx/src/main/scala/org/apache/spark/graphx/Pregel.scala ---
@@ -22,12 +22,58 @@ import org.apache.spark.Logging
/**
- * Implements a Pregel-like bulk-synchronous message-passing API.
+ * The Pregel Vertex class contains the vertex attribute and the boolean
flag
+ * indicating whether the vertex is active.
*
- * Unlike the original Pregel API, the GraphX Pregel API factors the
sendMessage computation over
- * edges, enables the message sending computation to read both vertex
attributes, and constrains
- * messages to the graph structure. These changes allow for substantially
more efficient
- * distributed execution while also exposing greater flexibility for
graph-based computation.
+ * @param attr the vertex prorperty during the pregel computation (e.g.,
+ * PageRank)
+ * @param isActive a flag indicating whether the vertex is active
+ * @tparam T the type of the vertex property
+ */
+sealed case class PregelVertex[@specialized T]
+ (attr: T, isActive: Boolean = true) extends Product2[T, Boolean] {
+ override def _1: T = attr
+ override def _2: Boolean = isActive
+}
+
+
+/**
+ * The Pregel API enables users to express iterative graph algorithms in
GraphX
+ * and is loosely based on the Google and GraphLab APIs.
+ *
+ * At a high-level iterative graph algorithms like PageRank recursively
define
+ * vertex properties in terms of the properties of neighboring vertices.
These
+ * recursive properties are then computed through iterative fixed-point
+ * computations. For example, the PageRank of a web-page can be defined
as a
+ * weighted some of the PageRank of web-pages that link to that page and is
--- End diff --
"weighted sum" :)
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