Even if you start with two vertices, the number of partitions is based on the number of workers squared multiplied by a multiplier (see HashMasterPartitioner#PARTITION_COUNT_MULTIPLIER). By default, the multiplier is 1, so if you have say 10 workers, you'll have 100 partitions. There is a maximum number of partitions though due to the max zknode size of about 2995. So everything should be fine for you.


On 2/10/12 1:52 PM, David Garcia wrote:
Ah, so, I think I would like to balance by vertices.  My main question is
that my graph starts with two vertices. . .I would like to specify more
than two mappers.  My job will end up creating around 100,000 vertices.  I
would like to make sure that these extra vertices will be evenly
distributed across all mappers (including the ones that don't have the
initial two vertices).  Does this make sense?  Does Giraph support this
out of the box, or do I need to add something?  Thx.


On 2/10/12 3:41 PM, "Avery Ching"<ach...@apache.org>  wrote:

By default, you are using the HashPartitionerFactory.  This will create
the partitions ahead of time and balance them equally by count to the
workers.  Therefore, assuming you have a uniform distribution across the
VertexId space, the graph should be balanced across the workers evenly
according the number of vertices.  If you look at PartitionBalancer, you
can try to rebalance the graph if you like as it is running.  This is a
bit experimental, but should work.  The choices for balancing are (no
balancing, balance by edges or balance by vertices).

Hope that helps,


On 2/10/12 1:25 PM, David Garcia wrote:
Hey guys. . .I have a questions about "dynamic" vertex instantiation vis
the sendMsg(. . .) method.  I have a job that starts processing on a
sequenceFile with only two vertices in it.  Each vertex has information
it's value that tells it what vertices are adjacent to it.  The primary
reason I'm doing this is to avoid loading the entire graph into the job.
There are many vertices that won't do any processing (no need to load
them).  I would like to take my two vertices and "dynamically" build the
graph by sending messages.  So far, my experimentation shows that this
promising. . .but I have a question WRT load balancing for new vertex
instantiation.  When I call sendMsg(newVertexID), where will the vertex
instantiated?  If I specify 20 mappers (but with only two vertices in my
sequence file), obviously there is going to be at least one mapper
a vertex.  Is it possible that sendMsg(newVertexID) will be instantiated
on an empty mapper?  I would like this. . .for load balancing purposes.


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