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From Lukas Nalezenec <lukas.naleze...@firma.seznam.cz>
Subject Re: concept of vertex in giraph
Date Fri, 25 Jul 2014 09:02:57 GMT
On 25.7.2014 10:56, Carmen Manzulli wrote:
> ah ok, thanksa lot!...so is the same for edgevalues and 
> targetvertexids??? i need to use combiners, can you show me where can 
> i read more information about?
>
>
I have never used the feature so I dont know much about it.

See source code.
For example ByteArrayPartition.java:183:

   /**
    * Combine two vertices together and store the serialized bytes
    * in the vertex map.
    *
    * @param representativeVertex existing vertex
    * @param representativeCombinerVertex new vertex to combine
    */
   private void combine(Vertex<I, V, E> representativeVertex,
       Vertex<I, V, E> representativeCombinerVertex) {
getVertexValueCombiner().combine(representativeVertex.getValue(),
         representativeCombinerVertex.getValue());
     // Add the edges to the representative vertex
     for (Edge<I, E> edge : representativeCombinerVertex.getEdges()) {
       representativeVertex.addEdge(edge);
     }
     vertexMap.put(representativeCombinerVertex.getId(),
         WritableUtils.writeVertexToByteArray(
             representativeVertex, useUnsafeSerialization, getConf()));
   }


By default Giraph uses DefaultVertexValueCombiner which does nothing.


> 2014-07-25 10:52 GMT+02:00 Lukas Nalezenec 
> <lukas.nalezenec@firma.seznam.cz 
> <mailto:lukas.nalezenec@firma.seznam.cz>>:
>
>     Hi,
>     Afaik vertex ids must be unique but you can combine vertexes with
>     same ID to one using VertexValueCombiner.
>
>     Lukas
>
>
>     On 25.7.2014 10:33, Carmen Manzulli wrote:
>>      Hi experts,
>>     i would like to ask you if , in the graph rapresentation, every
>>     time a vertexId is reapeated, would giraph consider just one time
>>     that vertexId?
>>
>>     for example:
>>
>>     Carmen (vertexId) 24 (vertex value) .....
>>     Carmen (vertexId) 1,60 m (vertex value)...
>>
>>     does it became
>>
>>     Carmen -->24
>>                 -->1,60
>>
>>     from a point of view conceptual?
>
>


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