Packages

object Pregel extends Logging

Implements a Pregel-like bulk-synchronous message-passing API.

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.

Source
Pregel.scala
Example:

  1. We can use the Pregel abstraction to implement PageRank:

    val pagerankGraph: Graph[Double, Double] = graph
  // Associate the degree with each vertex
  .outerJoinVertices(graph.outDegrees) {
    (vid, vdata, deg) => deg.getOrElse(0)
  }
  // Set the weight on the edges based on the degree
  .mapTriplets(e => 1.0 / e.srcAttr)
  // Set the vertex attributes to the initial pagerank values
  .mapVertices((id, attr) => 1.0)

def vertexProgram(id: VertexId, attr: Double, msgSum: Double): Double =
  resetProb + (1.0 - resetProb) * msgSum
def sendMessage(id: VertexId, edge: EdgeTriplet[Double, Double]): Iterator[(VertexId, Double)] =
  Iterator((edge.dstId, edge.srcAttr * edge.attr))
def messageCombiner(a: Double, b: Double): Double = a + b
val initialMessage = 0.0
// Execute Pregel for a fixed number of iterations.
Pregel(pagerankGraph, initialMessage, numIter)(
  vertexProgram, sendMessage, messageCombiner)
Linear Supertypes
Logging, AnyRef, Any
Ordering
  1. Alphabetic
  2. By Inheritance
Inherited
  1. Pregel
  2. Logging
  3. AnyRef
  4. Any
  1. Hide All
  2. Show All
Visibility
  1. Public
  2. Protected

Type Members

  1. implicit class LogStringContext extends AnyRef
    Definition Classes
    Logging

Value Members

  1. final def !=(arg0: Any): Boolean
    Definition Classes
    AnyRef → Any
  2. final def ##: Int
    Definition Classes
    AnyRef → Any
  3. final def ==(arg0: Any): Boolean
    Definition Classes
    AnyRef → Any
  4. def MDC(key: LogKey, value: Any): MDC
    Attributes
    protected
    Definition Classes
    Logging
  5. def apply[VD, ED, A](graph: Graph[VD, ED], initialMsg: A, maxIterations: Int = Int.MaxValue, activeDirection: EdgeDirection = EdgeDirection.Either)(vprog: (VertexId, VD, A) => VD, sendMsg: (EdgeTriplet[VD, ED]) => Iterator[(VertexId, A)], mergeMsg: (A, A) => A)(implicit arg0: ClassTag[VD], arg1: ClassTag[ED], arg2: ClassTag[A]): Graph[VD, ED]

    Execute a Pregel-like iterative vertex-parallel abstraction.

    Execute a Pregel-like iterative vertex-parallel abstraction. The user-defined vertex-program vprog is executed in parallel on each vertex receiving any inbound messages and computing a new value for the vertex. The sendMsg function is then invoked on all out-edges and is used to compute an optional message to the destination vertex. The mergeMsg function is a commutative associative function used to combine messages destined to the same vertex.

    On the first iteration all vertices receive the initialMsg and on subsequent iterations if a vertex does not receive a message then the vertex-program is not invoked.

    This function iterates until there are no remaining messages, or for maxIterations iterations.

    VD

    the vertex data type

    ED

    the edge data type

    A

    the Pregel message type

    graph

    the input graph.

    initialMsg

    the message each vertex will receive at the first iteration

    maxIterations

    the maximum number of iterations to run for

    activeDirection

    the direction of edges incident to a vertex that received a message in the previous round on which to run sendMsg. For example, if this is EdgeDirection.Out, only out-edges of vertices that received a message in the previous round will run. The default is EdgeDirection.Either, which will run sendMsg on edges where either side received a message in the previous round. If this is EdgeDirection.Both, sendMsg will only run on edges where *both* vertices received a message.

    vprog

    the user-defined vertex program which runs on each vertex and receives the inbound message and computes a new vertex value. On the first iteration the vertex program is invoked on all vertices and is passed the default message. On subsequent iterations the vertex program is only invoked on those vertices that receive messages.

    sendMsg

    a user supplied function that is applied to out edges of vertices that received messages in the current iteration

    mergeMsg

    a user supplied function that takes two incoming messages of type A and merges them into a single message of type A. This function must be commutative and associative and ideally the size of A should not increase.

    returns

    the resulting graph at the end of the computation

  6. final def asInstanceOf[T0]: T0
    Definition Classes
    Any
  7. def clone(): AnyRef
    Attributes
    protected[lang]
    Definition Classes
    AnyRef
    Annotations
    @throws(classOf[java.lang.CloneNotSupportedException]) @IntrinsicCandidate() @native()
  8. final def eq(arg0: AnyRef): Boolean
    Definition Classes
    AnyRef
  9. def equals(arg0: AnyRef): Boolean
    Definition Classes
    AnyRef → Any
  10. final def getClass(): Class[_ <: AnyRef]
    Definition Classes
    AnyRef → Any
    Annotations
    @IntrinsicCandidate() @native()
  11. def hashCode(): Int
    Definition Classes
    AnyRef → Any
    Annotations
    @IntrinsicCandidate() @native()
  12. def initializeLogIfNecessary(isInterpreter: Boolean, silent: Boolean): Boolean
    Attributes
    protected
    Definition Classes
    Logging
  13. def initializeLogIfNecessary(isInterpreter: Boolean): Unit
    Attributes
    protected
    Definition Classes
    Logging
  14. final def isInstanceOf[T0]: Boolean
    Definition Classes
    Any
  15. def isTraceEnabled(): Boolean
    Attributes
    protected
    Definition Classes
    Logging
  16. def log: Logger
    Attributes
    protected
    Definition Classes
    Logging
  17. def logBasedOnLevel(level: Level)(f: => MessageWithContext): Unit
    Attributes
    protected
    Definition Classes
    Logging
  18. def logDebug(msg: => String, throwable: Throwable): Unit
    Attributes
    protected
    Definition Classes
    Logging
  19. def logDebug(entry: LogEntry, throwable: Throwable): Unit
    Attributes
    protected
    Definition Classes
    Logging
  20. def logDebug(entry: LogEntry): Unit
    Attributes
    protected
    Definition Classes
    Logging
  21. def logDebug(msg: => String): Unit
    Attributes
    protected
    Definition Classes
    Logging
  22. def logError(msg: => String, throwable: Throwable): Unit
    Attributes
    protected
    Definition Classes
    Logging
  23. def logError(entry: LogEntry, throwable: Throwable): Unit
    Attributes
    protected
    Definition Classes
    Logging
  24. def logError(entry: LogEntry): Unit
    Attributes
    protected
    Definition Classes
    Logging
  25. def logError(msg: => String): Unit
    Attributes
    protected
    Definition Classes
    Logging
  26. def logInfo(msg: => String, throwable: Throwable): Unit
    Attributes
    protected
    Definition Classes
    Logging
  27. def logInfo(entry: LogEntry, throwable: Throwable): Unit
    Attributes
    protected
    Definition Classes
    Logging
  28. def logInfo(entry: LogEntry): Unit
    Attributes
    protected
    Definition Classes
    Logging
  29. def logInfo(msg: => String): Unit
    Attributes
    protected
    Definition Classes
    Logging
  30. def logName: String
    Attributes
    protected
    Definition Classes
    Logging
  31. def logTrace(msg: => String, throwable: Throwable): Unit
    Attributes
    protected
    Definition Classes
    Logging
  32. def logTrace(entry: LogEntry, throwable: Throwable): Unit
    Attributes
    protected
    Definition Classes
    Logging
  33. def logTrace(entry: LogEntry): Unit
    Attributes
    protected
    Definition Classes
    Logging
  34. def logTrace(msg: => String): Unit
    Attributes
    protected
    Definition Classes
    Logging
  35. def logWarning(msg: => String, throwable: Throwable): Unit
    Attributes
    protected
    Definition Classes
    Logging
  36. def logWarning(entry: LogEntry, throwable: Throwable): Unit
    Attributes
    protected
    Definition Classes
    Logging
  37. def logWarning(entry: LogEntry): Unit
    Attributes
    protected
    Definition Classes
    Logging
  38. def logWarning(msg: => String): Unit
    Attributes
    protected
    Definition Classes
    Logging
  39. final def ne(arg0: AnyRef): Boolean
    Definition Classes
    AnyRef
  40. final def notify(): Unit
    Definition Classes
    AnyRef
    Annotations
    @IntrinsicCandidate() @native()
  41. final def notifyAll(): Unit
    Definition Classes
    AnyRef
    Annotations
    @IntrinsicCandidate() @native()
  42. final def synchronized[T0](arg0: => T0): T0
    Definition Classes
    AnyRef
  43. def toString(): String
    Definition Classes
    AnyRef → Any
  44. final def wait(arg0: Long, arg1: Int): Unit
    Definition Classes
    AnyRef
    Annotations
    @throws(classOf[java.lang.InterruptedException])
  45. final def wait(arg0: Long): Unit
    Definition Classes
    AnyRef
    Annotations
    @throws(classOf[java.lang.InterruptedException]) @native()
  46. final def wait(): Unit
    Definition Classes
    AnyRef
    Annotations
    @throws(classOf[java.lang.InterruptedException])
  47. def withLogContext(context: Map[String, String])(body: => Unit): Unit
    Attributes
    protected
    Definition Classes
    Logging

Deprecated Value Members

  1. def finalize(): Unit
    Attributes
    protected[lang]
    Definition Classes
    AnyRef
    Annotations
    @throws(classOf[java.lang.Throwable]) @Deprecated
    Deprecated

    (Since version 9)

Inherited from Logging

Inherited from AnyRef

Inherited from Any

Ungrouped