On 07.12.2014 18:08, Alessandro wrote:

Hello, I want to try graph-tool because it seems a very powerful and fast way to work with graphs in python.

I installed it with the pre-compiled package for ubuntu 14.04 on a 32 bit machine. I tested this code

from graph_tool.all import *

g = Graph() v1 = g.add_vertex() v2 = g.add_vertex() v3 = g.add_vertex() v4 = g.add_vertex() v5 = g.add_vertex()

e1 = g.add_edge(v1, v5) e2 = g.add_edge(v2, v3) e3 = g.add_edge(v3, v4) e4 = g.add_edge(v4, v2) e5 = g.add_edge(v4, v5) e6 = g.add_edge(v4, v1)

weights = g.new_edge_property("int") weights[e1] = 2 weights[e2] = 3 weights[e3] = 2 weights[e4] = -1 weights[e5] = 5 weights[e6] = 1

minimized, dist, pred = bellman_ford_search(g, g.vertex(0), weights)

and what I get is:

File "/usr/lib/python2.7/dist-packages/graph_tool/search/__init__.py", line 1118, in bellman_ford_search zero, infinity) OverflowError: Python int too large to convert to C long.

In case I add the infinity parameter, so minimized, dist, pred = bellman_ford_search(g, g.vertex(0), weights, infinity=int)

I get

File "graphTest2.py", line 26, in <module> minimized, dist, pred = bellman_ford_search(g, g.vertex(0), weights, infinity=int) File "/usr/lib/python2.7/dist-packages/graph_tool/search/__init__.py", line 1103, in bellman_ford_search infinity = _python_type(dist_map.value_type())(infinity) TypeError: descriptor '__trunc__' of 'int' object needs an argument

and the same happens with infinity=float.

I tested dijkstra_search, that uses infinity as well, but I don't get any problem.

Could you please tell me if I am doing something wrong, or if there is a problem?

The 'infinity' option expects the _value_ not the type of infinity. Since you are using an integer-valued map, you should use something like infinity=((1 << 31) - 1). Best, Tiago -- Tiago de Paula Peixoto <tiago@skewed.de>