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From "Yuanyuan Tian (Created) (JIRA)" <j...@apache.org>
Subject [jira] [Created] (GIRAPH-125) Bug in LongDoubleFloatDoubleVertex.sendMsgToAllEdges()
Date Wed, 18 Jan 2012 01:53:39 GMT
Bug in LongDoubleFloatDoubleVertex.sendMsgToAllEdges()
------------------------------------------------------

                 Key: GIRAPH-125
                 URL: https://issues.apache.org/jira/browse/GIRAPH-125
             Project: Giraph
          Issue Type: Bug
          Components: graph
    Affects Versions: 0.1.0
            Reporter: Yuanyuan Tian


I just found a bug in the sendMsgToAllEdges() function of the LongDoubleFloatDoubleVertex
class. The segment of the code that contains the bug is:

        final LongWritable destVertex = new LongWritable();
        final MutableVertex<LongWritable, DoubleWritable, FloatWritable,
            DoubleWritable> vertex = this;
        verticesWithEdgeValues.forEachKey(new LongProcedure() {
            @Override
            public boolean apply(long destVertexId) {
                destVertex.set(destVertexId);
                vertex.sendMsg(destVertex, msg);
                return true;
            }
        });

Here destVertex is a final object, but this single object is reused in the forEachKey function
many times. Each time its actual value is changed but the same object is put to the underlying
message list (a hashmap) through vertex.sendMsg. Because the single destVertex object has
been put into the underlying hashmap again and again, destVertex.set(destVertexId) will change
the existing keys in the hashmap. Eventually, every keys added to the hash map will have the
same value as the last key. 

A simple fix is as follows:

        final MutableVertex<LongWritable, DoubleWritable, FloatWritable,
            DoubleWritable> vertex = this;
        verticesWithEdgeValues.forEachKey(new LongProcedure() {
            @Override
            public boolean apply(long destVertexId) {
                vertex.sendMsg(new LongWritable(destVertexId), msg);
                return true;
            }
        });

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