Use undirected edges instead of iterating

lib/mosaik/extractors/evolution.rb

@@ -80,16 +80,15 @@ def call
 
         info "Constructing contributor coupling graph..."
 
-        # FIXME: add undirected edges instead of iterating over all permutation
-        contributors.keys.permutation(2).each do |(a, b)|
-          next if contributors[a].empty? || contributors[b].empty?
+        contributors.keys.each do |(a, b)|
+          next if a == b || contributors[a].empty? || contributors[b].empty?
 
           graph.find_or_add_vertex(a)
           graph.find_or_add_vertex(b)
 
           # Add a weighted edge to the graph (weight is the cardinality of the intersection of sets)
           # FIXME: aggregate with existing edges
-          graph.add_directed_edge(a, b, weight: (contributors[a] & contributors[b]).count * options[:contributor])
+          graph.add_undirected_edge(a, b, weight: (contributors[a] & contributors[b]).count * options[:contributor])
         end
       end