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From "Schweiger, Tom" <>
Subject RE: concept of vertex in giraph
Date Fri, 25 Jul 2014 16:47:09 GMT
Edges "combine" differently than vertexes.

By default, each edge you read is added to the adjacency set of the source vertex (all edges
are directed in Giraph, if you had not realized that yet).  So if you read multiple edge for
the same source -> target, they will all be represented in the source vertex's edges.

If you actually need to combine edges there are two way to go about it.

1) (easy but unelegant) deal with the fact in your compute

2) (more involved but efficient) write your own OutEdges class, unless one already exists
that does what you need.

From: Carmen Manzulli []
Sent: Friday, July 25, 2014 1:56 AM
Subject: Re: concept of vertex in giraph

ah ok, thanksa lot! is the same for edgevalues and targetvertexids??? i need to use combiners,
can you show me where can i read more information about?

2014-07-25 10:52 GMT+02:00 Lukas Nalezenec <<>>:
Afaik vertex ids must be unique but you can combine vertexes with same ID to one using VertexValueCombiner.


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

from a point of view conceptual?

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