Model Graph.gaml often throws Illegal Argument error when calculating shortest path

[lesquoyb]

Describe the bug When clicking on the button "Path with Graph" in the model Graph.gaml from Models Library There's often an illegal argument exception raised by gama. It sometimes takes a few tries but it is very frequent.

Here is the message I have in the user interface:

2 occurrences in 2 agents at cycle 15: Java error: illegal argument
in Graph0
in map<int, geometry> mfb <- map<int, geometry>(max_flow_between(g_graph,node1,node2));
IllegalArgumentException: source is equal to sink
org.jgrapht.alg.flow.EdmondsKarpMFImpl.calculateMaximumFlow(EdmondsKarpMFImpl.java:164)
org.jgrapht.alg.flow.EdmondsKarpMFImpl.getMaximumFlow(EdmondsKarpMFImpl.java:135)
gama.gaml.operators.Graphs.maxFlowBetween(Graphs.java:2453)
gaml.additions.core.GamlAdditions.lambda$624(GamlAdditions.java:677)
gama.gaml.expressions.operators.AbstractNAryOperator._value(AbstractNAryOperator.java:388)
gama.gaml.expressions.AbstractExpression.value(AbstractExpression.java:87)
gama.gaml.expressions.operators.BinaryOperator._value(BinaryOperator.java:148)
when applying the max_flow_between operator on [graph { 
vertices (10): [0,1,2,3,4,5,6,7,8,9,]
edges (45): [
regular_agent_edge0 (0 -> 1),
regular_agent_edge1 (0 -> 2),
regular_agent_edge2 (0 -> 3),
regular_agent_edge3 (0 -> 4),
regular_agent_edge4 (0 -> 5),
regular_agent_edge5 (0 -> 6),
regular_agent_edge6 (0 -> 7),
regular_agent_edge7 (0 -> 8),
regular_agent_edge8 (0 -> 9),
regular_agent_edge9 (1 -> 2),
regular_agent_edge10    (1 -> 3),
regular_agent_edge11    (1 -> 4),
regular_agent_edge12    (1 -> 5),
regular_agent_edge13    (1 -> 6),
regular_agent_edge14    (1 -> 7),
regular_agent_edge15    (1 -> 8),
regular_agent_edge16    (1 -> 9),
regular_agent_edge17    (2 -> 3),
regular_agent_edge18    (2 -> 4),
regular_agent_edge19    (2 -> 5),
regular_agent_edge20    (2 -> 6),
regular_agent_edge21    (2 -> 7),
regular_agent_edge22    (2 -> 8),
regular_agent_edge23    (2 -> 9),
regular_agent_edge24    (3 -> 4),
regular_agent_edge25    (3 -> 5),
regular_agent_edge26    (3 -> 6),
regular_agent_edge27    (3 -> 7),
regular_agent_edge28    (3 -> 8),
regular_agent_edge29    (3 -> 9),
regular_agent_edge30    (4 -> 5),
regular_agent_edge31    (4 -> 6),
regular_agent_edge32    (4 -> 7),
regular_agent_edge33    (4 -> 8),
regular_agent_edge34    (4 -> 9),
regular_agent_edge35    (5 -> 6),
regular_agent_edge36    (5 -> 7),
regular_agent_edge37    (5 -> 8),
regular_agent_edge38    (5 -> 9),
regular_agent_edge39    (6 -> 7),
regular_agent_edge40    (6 -> 8),
regular_agent_edge41    (6 -> 9),
regular_agent_edge42    (7 -> 8),
regular_agent_edge43    (7 -> 9),
regular_agent_edge44    (8 -> 9),
]
}, 9, 9]
in map<int, geometry> mfb <- map<int, geometry>(max_flow_between(g_graph,node1,node2));
in action path_finding_graph  {
    write '
    ====================' ;
    write 'GRAPH PATH OPERATORS
    ' ;
    write 'The matrix of predecessor in all shortest path: ' ;
    matrix<int> sp <- all_pairs_shortest_path(g_graph);
    write first(10,sp) ;
    g_graph <- load_shortest_paths(g_graph,sp);
    geometry node1 <- any(g_graph.vertices);
    geometry node2 <- any(g_graph.vertices);
    map<int, geometry> mfb <- map<int, geometry>(max_flow_between(g_graph,node1,node2));
    write 'Find a path between two nodes: \'graph path_between (node1, node2)\'' ;
    the_path <- path_between(g_graph,node1,node2);
}

in do path_finding_graph ;
in ask world  {
    do path_finding_graph ;
}

in ask world  {
    do path_finding_graph ;
}

in user_command 'Path with graph'  {
    ask world  {
        do path_finding_graph ;
    }

}

in agents Simulation 0, Graph0

It may be related to some threading issue as it's easier to get it when double clicking (or probably more) on the button