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From Yuanyuan Tian <yt...@us.ibm.com>
Subject problem using LongDoubleFloatDoubleVertex
Date Wed, 21 Dec 2011 02:07:42 GMT


Hi,

I decided to use LongDoubleFloatDoubleVertex in a graph algorithm because
it uses more compact and efficient mahout collections. However I run into
an error when running the algorithm:

java.lang.ClassCastException: org.apache.giraph.graph.
LongDoubleFloatDoubleVertex cannot be cast to
org.apache.giraph.graph.Vertex
		 at
org.apache.giraph.comm.BasicRPCCommunications.prepareSuperstep
(BasicRPCCommunications.java:1016)
		 at org.apache.giraph.graph.BspServiceWorker.startSuperstep
(BspServiceWorker.java:843)
		 at org.apache.giraph.graph.GraphMapper.map
(GraphMapper.java:569)
		 at org.apache.giraph.graph.GraphMapper.run
(GraphMapper.java:728)
		 ... 7 more

Basically, the problem is that in BasicRPCCommunications.prepareSuperStep
(), the LongDoubleFloatDoubleVertex are cast to Vertex in the following
code fragment. But LongDoubleFloatDoubleVertex inherits from BasicVertex
instead of Vertex.

if (vertex != null) {
   ((MutableVertex<I, V, E, M>) vertex).setVertexId(vertexIndex);
   partition.putVertex((Vertex<I, V, E, M>) vertex);
} else if (originalVertex != null) {
  partition.removeVertex(originalVertex.getVertexId());
}

I did a simple change: cast LongDoubleFloatDoubleVertex to BasicVertex. The
problem went away, and the algorithm finished without any error. But I am
not sure this change has any implication to other parts of the code. So, I
hope to get some comments from the Giraph developers.

if (vertex != null) {
   ((MutableVertex<I, V, E, M>) vertex).setVertexId(vertexIndex);
   partition.putVertex((BasicVertex<I, V, E, M>) vertex);
} else if (originalVertex != null) {
  partition.removeVertex(originalVertex.getVertexId());
}

Thanks,
Yuanyuan Tian
Research Staff Member
IBM Almaden Research Center
650 Harry Road
San Jose, California 95120-6099
(408) 927-1704
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