Remove double edge insertions

src/graph_functions.jl

@@ -135,13 +135,12 @@ function insert_edge!(graph::DAG, edge::Edge, track=true)
    node2 = edge.edge[2]
 
    # 1: mute
-   if (node2 in node1.parents) || (node1 in node2.children)
-      #=if !(node2 in node1.parents && node1 in node2.children)
+   #=if (node2 in node1.parents) || (node1 in node2.children)
+      if !(node2 in node1.parents && node1 in node2.children)
          error("One-sided edge")
-      end=#
-
-      return edge
-   end
+      end
+      error("Edge to insert already exists")
+   end=#
 
    # edge points from child to parent
    push!(node1.parents, node2)
@@ -276,7 +275,7 @@ function can_reduce(n1::Node, n2::Node)
    if (n1.task != n2.task)
       return false
    end
-   return Set(children(n1)) == Set(children(n2))
+   return Set(n1.children) == Set(n2.children)
 end
 
 function can_split(n::Node)
@@ -293,8 +292,7 @@ function is_valid(graph::DAG)
       current = pop!(nodeQueue)
       push!(seenNodes, current)
 
-      childrenNodes = children(current)
-      for child in childrenNodes
+      for child in current.chlidren
          push!(nodeQueue, child)
       end
    end

src/graph_operations.jl

@@ -155,15 +155,22 @@ function node_fusion!(graph::DAG, n1::ComputeTaskNode, n2::DataTaskNode, n3::Com
    new_node = ComputeTaskNode(FusedComputeTask{typeof(n1.task), typeof(n3.task)}())
    insert_node!(graph, new_node)
    
-   # "repoint" children of n1 to the new node
+   # use a set for combined children of n1 and n3 to not get duplicates
+   n1and3_children = Set{Node}()
+
+   # remove edges from n1 children to n1
    for child in n1_children
       remove_edge!(graph, make_edge(child, n1))
-      insert_edge!(graph, make_edge(child, new_node))
+      push!(n1and3_children, child)
    end
 
-   # "repoint" children of n3 to the new node
+   # remove edges from n3 children to n3
    for child in n3_children
       remove_edge!(graph, make_edge(child, n3))
+      push!(n1and3_children, child)
+   end
+
+   for child in n1and3_children
       insert_edge!(graph, make_edge(child, new_node))
    end
 
@@ -190,9 +197,9 @@ function node_reduction!(graph::DAG, n1::Node, n2::Node)
 
    # save n2 parents and children
    n2_children = children(n2)
-   n2_parents = parents(n2)
+   n2_parents = Set(n2.parents)
 
-   #=if Set(n2_children) != Set(children(n1))
+   #=if Set(n2_children) != Set(n1.children)
       error("[Node Reduction] The given nodes do not have equal prerequisite nodes which is required for node reduction")
    end=#
 
@@ -200,12 +207,22 @@ function node_reduction!(graph::DAG, n1::Node, n2::Node)
    for child in n2_children
       remove_edge!(graph, make_edge(child, n2))
    end
+
+
    for parent in n2_parents
       remove_edge!(graph, make_edge(n2, parent))
+   end
 
-      # add parents of n2 to n1
+   for parent in n1.parents
+      # delete parents in n1 that already exist in n2
+      delete!(n2_parents, parent)
+   end
+
+   for parent in n2_parents
+      # now add parents of n2 to n1 without duplicates
       insert_edge!(graph, make_edge(n1, parent))
    end
+
    remove_node!(graph, n2)
 
    return get_snapshot_diff(graph)
@@ -355,12 +372,10 @@ function find_reductions!(graph::DAG, node::Node)
 end
 
 function find_splits!(graph::DAG, node::Node)
-   for node in graph.nodes
-      if (can_split(node))
-         ns = NodeSplit(node)
-         push!(graph.possibleOperations.nodeSplits, ns)
-         push!(node.operations, ns)
-      end
+   if (can_split(node))
+      ns = NodeSplit(node)
+      push!(graph.possibleOperations.nodeSplits, ns)
+      push!(node.operations, ns)
    end
 
    return nothing