Hi Claudio, answers inline:
On 1/6/12 8:25 AM, Claudio Martella wrote:
Hello,
I hope somebody can shed some light on a piece of code i'm looking at
while working on GIRAPH-45 (and this code is also the object of
GIRAPH-95, so we'd probably get two birds with one stone here).
The code is taking care of vertex resolving in
BasicRPCCommunication::prepareSuperstep():
[line 1091]:
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());
}
First, vertex cannot be null as it's resolved by vertexRevolver, but i
guess it's a sanity check. But the real question is: why would you
setVertex() considering it's been already initialized correctly in
vertexResolver?
Actually it can be null. Since user's can implement their own vertex
resolver, they are allowed to return null from the javadoc.
/**
* A vertex may have been removed, created zero or more times and had
* zero or more messages sent to it. This method will handle all
situations
* excluding the normal case (a vertex already exists and has zero
or more
* messages sent it to).
*
* @param vertexId Vertex id (can be used for {@link BasicVertex}'s
* initialize())
* @param vertex Original vertex or null if none
* @param vertexChanges Changes that happened to this vertex or
null if none
* @param messages messages received in the last superstep or null
if none
* @return Vertex to be returned, if null, and a vertex currently
exists
* it will be removed
*/
Am I missing something or did I just realize that GIRAPH-95 is solved
by just removing that line? :)
Thanks
Well, not sure about that. The set is done there I think to ensure
safety. Here's the issue: Suppose that the resolve() doesn't set the
vertex id correctly (i.e. in this partition). That would be a bug and
probably cause issues. Probably this should be changed to be a check
though. Something like...
if (vertex != null) {
if (vertex.getVertexId().equals(vertexIndex)) {
throw new
IllegalStateException("BasicRPCCommunications: Illegal to set the vertex
index differently from " + vertexIndex);
if (originalVertex == null) {
partition.putVertex((BasicVertex<I, V, E, M>) vertex);
} else {
partition.removeVertex(originalVertex.getVertexId());
}
}
What do you think?
Avery