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<div class="subTitle">org.apache.spark.graphx</div>
<h2 title="Class Pregel" class="title">Class Pregel</h2>
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<li>java.lang.Object</li>
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<li>org.apache.spark.graphx.Pregel</li>
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<pre>public class <span class="strong">Pregel</span>
extends java.lang.Object
implements <a href="../../../../org/apache/spark/Logging.html" title="interface in org.apache.spark">Logging</a></pre>
<div class="block">Implements a Pregel-like bulk-synchronous message-passing API.
<p>
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.
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<td class="colOne"><code><strong><a href="../../../../org/apache/spark/graphx/Pregel.html#Pregel()">Pregel</a></strong>()</code> </td>
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<td class="colFirst"><code>static <VD,ED,A> <a href="../../../../org/apache/spark/graphx/Graph.html" title="class in org.apache.spark.graphx">Graph</a><VD,ED></code></td>
<td class="colLast"><code><strong><a href="../../../../org/apache/spark/graphx/Pregel.html#apply(org.apache.spark.graphx.Graph, A, int, org.apache.spark.graphx.EdgeDirection, scala.Function3, scala.Function1, scala.Function2, scala.reflect.ClassTag, scala.reflect.ClassTag, scala.reflect.ClassTag)">apply</a></strong>(<a href="../../../../org/apache/spark/graphx/Graph.html" title="class in org.apache.spark.graphx">Graph</a><VD,ED> graph,
A initialMsg,
int maxIterations,
<a href="../../../../org/apache/spark/graphx/EdgeDirection.html" title="class in org.apache.spark.graphx">EdgeDirection</a> activeDirection,
scala.Function3<java.lang.Object,VD,A,VD> vprog,
scala.Function1<<a href="../../../../org/apache/spark/graphx/EdgeTriplet.html" title="class in org.apache.spark.graphx">EdgeTriplet</a><VD,ED>,scala.collection.Iterator<scala.Tuple2<java.lang.Object,A>>> sendMsg,
scala.Function2<A,A,A> mergeMsg,
scala.reflect.ClassTag<VD> evidence$1,
scala.reflect.ClassTag<ED> evidence$2,
scala.reflect.ClassTag<A> evidence$3)</code>
<div class="block">Execute a Pregel-like iterative vertex-parallel abstraction.</div>
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<code><a href="../../../../org/apache/spark/Logging.html#initializeIfNecessary()">initializeIfNecessary</a>, <a href="../../../../org/apache/spark/Logging.html#initializeLogging()">initializeLogging</a>, <a href="../../../../org/apache/spark/Logging.html#isTraceEnabled()">isTraceEnabled</a>, <a href="../../../../org/apache/spark/Logging.html#log_()">log_</a>, <a href="../../../../org/apache/spark/Logging.html#log()">log</a>, <a href="../../../../org/apache/spark/Logging.html#logDebug(scala.Function0)">logDebug</a>, <a href="../../../../org/apache/spark/Logging.html#logDebug(scala.Function0, java.lang.Throwable)">logDebug</a>, <a href="../../../../org/apache/spark/Logging.html#logError(scala.Function0)">logError</a>, <a href="../../../../org/apache/spark/Logging.html#logError(scala.Function0, java.lang.Throwable)">logError</a>, <a href="../../../../org/apache/spark/Logging.html#logInfo(scala.Function0)">logInfo</a>, <a href="../../../../org/apache/spark/Logging.html#logInfo(scala.Function0, java.lang.Throwable)">logInfo</a>, <a href="../../../../org/apache/spark/Logging.html#logName()">logName</a>, <a href="../../../../org/apache/spark/Logging.html#logTrace(scala.Function0)">logTrace</a>, <a href="../../../../org/apache/spark/Logging.html#logTrace(scala.Function0, java.lang.Throwable)">logTrace</a>, <a href="../../../../org/apache/spark/Logging.html#logWarning(scala.Function0)">logWarning</a>, <a href="../../../../org/apache/spark/Logging.html#logWarning(scala.Function0, java.lang.Throwable)">logWarning</a></code></li>
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<h4>Pregel</h4>
<pre>public Pregel()</pre>
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<a name="apply(org.apache.spark.graphx.Graph,java.lang.Object,int,org.apache.spark.graphx.EdgeDirection,scala.Function3,scala.Function1,scala.Function2,scala.reflect.ClassTag,scala.reflect.ClassTag,scala.reflect.ClassTag)">
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<h4>apply</h4>
<pre>public static <VD,ED,A> <a href="../../../../org/apache/spark/graphx/Graph.html" title="class in org.apache.spark.graphx">Graph</a><VD,ED> apply(<a href="../../../../org/apache/spark/graphx/Graph.html" title="class in org.apache.spark.graphx">Graph</a><VD,ED> graph,
A initialMsg,
int maxIterations,
<a href="../../../../org/apache/spark/graphx/EdgeDirection.html" title="class in org.apache.spark.graphx">EdgeDirection</a> activeDirection,
scala.Function3<java.lang.Object,VD,A,VD> vprog,
scala.Function1<<a href="../../../../org/apache/spark/graphx/EdgeTriplet.html" title="class in org.apache.spark.graphx">EdgeTriplet</a><VD,ED>,scala.collection.Iterator<scala.Tuple2<java.lang.Object,A>>> sendMsg,
scala.Function2<A,A,A> mergeMsg,
scala.reflect.ClassTag<VD> evidence$1,
scala.reflect.ClassTag<ED> evidence$2,
scala.reflect.ClassTag<A> evidence$3)</pre>
<div class="block">Execute a Pregel-like iterative vertex-parallel abstraction. The
user-defined vertex-program <code>vprog</code> is executed in parallel on
each vertex receiving any inbound messages and computing a new
value for the vertex. The <code>sendMsg</code> function is then invoked on
all out-edges and is used to compute an optional message to the
destination vertex. The <code>mergeMsg</code> function is a commutative
associative function used to combine messages destined to the
same vertex.
<p>
On the first iteration all vertices receive the <code>initialMsg</code> and
on subsequent iterations if a vertex does not receive a message
then the vertex-program is not invoked.
<p>
This function iterates until there are no remaining messages, or
for <code>maxIterations</code> iterations.
<p></div>
<dl><dt><span class="strong">Parameters:</span></dt><dd><code>graph</code> - the input graph.
<p></dd><dd><code>initialMsg</code> - the message each vertex will receive at the first
iteration
<p></dd><dd><code>maxIterations</code> - the maximum number of iterations to run for
<p></dd><dd><code>activeDirection</code> - the direction of edges incident to a vertex that received a message in
the previous round on which to run <code>sendMsg</code>. For example, if this is <code>EdgeDirection.Out</code>, only
out-edges of vertices that received a message in the previous round will run. The default is
<code>EdgeDirection.Either</code>, which will run <code>sendMsg</code> on edges where either side received a message
in the previous round. If this is <code>EdgeDirection.Both</code>, <code>sendMsg</code> will only run on edges where
*both* vertices received a message.
<p></dd><dd><code>vprog</code> - 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.
<p></dd><dd><code>sendMsg</code> - a user supplied function that is applied to out
edges of vertices that received messages in the current
iteration
<p></dd><dd><code>mergeMsg</code> - 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.''
<p></dd><dd><code>evidence$1</code> - (undocumented)</dd><dd><code>evidence$2</code> - (undocumented)</dd><dd><code>evidence$3</code> - (undocumented)</dd>
<dt><span class="strong">Returns:</span></dt><dd>the resulting graph at the end of the computation
<p></dd></dl>
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