On 09.01.2018 02:28, Percy wrote:
Hello, Tiago!
A small example to reproduce the problem please find as the following.
import multiprocess as mp import graph_tool.all as gt import numpy as np
g = gt.price_network(20, m = 2, directed = False) valid_paths = g.new_vertex_property("object") g.vertex_properties["valid_paths"] = valid_paths
Cloudlet = [] Gateway = [] for v in g.vertices(): if np.random.rand() > 0.5: Cloudlet.append(v) else: Gateway.append(v)
pool = mp.Pool(processes=4) for v in Gateway: valid_paths[v] = pool.map(lambda x: gt.all_shortest_paths(g = g, source = g.vertex_index[v], target = x),[g.vertex_index[c] for c in Cloudlet])
The version of my graph-tool is 2.25. Now, the python compiler says
MaybeEncodingError: Error sending result: '[<graph_tool.libgraph_tool_core.CoroGenerator object at 0x7f344b5f4f80>]'. Reason: 'RuntimeError('Pickling of "graph_tool.libgraph_tool_core.CoroGenerator" instances is not enabled (http://www.boost.org/libs/python/doc/v2/pickle.html)',)'
I know vertex objects cannot be picked. However, I think I have converted vertex objects into a int list before sending them to map function, i.e., "[g.vertex_index[c] for c in Cloudlet]". In particular, we can print [g.vertex_index[c] for c in Cloudlet], and terminal shows something like [1,2,3,4,5].
Is there any thing I misunderstand ?
As the error says, the iterator objects returned by all_shortest_paths() cannot be pickled. The values returned by the function fed to pool.map() must be pickable. Hence you need to convert the iterator to lists or something else before returning. -- Tiago de Paula Peixoto <tiago@skewed.de>