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