minimum cost MCP with IPython Parallel

[OOM]

Hi,

I am trying to use graph.MCP_Geometric(costs) on a cluster. The script and 
methods I use work on my personal computer which has 64GB memory. I am now 
trying to implement the same code on a cluster using IPython parallel. 
Here's the problem, each node/task only has about 20GB memory so they 
cannot even complete the 

mcp=graph.MCP_Geometric(costs)

command. My cost data has shape (12837, 43345). 

I am trying IPython parallel since I think it should allow me to overcome 
the lack of memory in each node. E.g. If I define a parallel function like

@dview.parallel(block=True)
def costsnx(costs):
    mcp=graph.MCP_Geometric(costs)
    return mcp

and run it

mcpp=costsnx(costs)

I get a list with mcp objects like <skimage.graph._mcp.MCP_Geometric at 
0x2d6fdd0>, one for each process I created. So in principle this would 
solve the memory problem, but the individual mcp objects do not seem to 
work e.g. executing 

mcpp[30].find_costs([[0,0]])

generates

TypeError: object of type 'NoneType' has no len()

Also, there is no way to join them to recreate the real graph. I tried also 
including the 

mcp.find_costs(location)

command in the parallel function, but it cannot find the location. I was 
thinking that perhaps there would be a way to use the intermediate steps of 
the graph.MCP_Geometric function to get the indices or something that could 
be constructed in parallel and then joined back into a unique element to 
compute minimum_costs.

Any ideas on how this could be implemented? Or any idea on how to tackle 
the problem at all?

I appreciate any help or pointers.

Thanks

OOM

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