Merge pull request #724 from milosgajdos83/efficient-bfs-queue

Make Nodes() BFS implementation efficient

network/default.go

@@ -1,6 +1,7 @@
 package network
 
 import (
+	"container/list"
 	"sync"
 	"time"
 
@@ -731,38 +732,31 @@ func (n *network) Connect() error {
 }
 
 // Nodes returns a list of all network nodes
-// NOTE: this is a naive i.e. inefficient BFS implementation
 func (n *network) Nodes() []Node {
-	// map to track visited nodes
+	//track the visited nodes
 	visited := make(map[string]*node)
 	// queue of the nodes to visit
-	queue := make([]*node, 1)
-	queue[0] = n.node
-	// add the root node to the map of the visited nodes
+	queue := list.New()
+	// push network node to the back of queue
+	queue.PushBack(n.node)
+	// mark the node as visited
 	visited[n.node.id] = n.node
 
-	for {
-		// pop a node from the queue
-		qnode := queue[0]
-		// pop is done by reslicing of the queue
-		// https://github.com/golang/go/wiki/SliceTricks
-		queue = queue[1:]
+	// keep iterating over the queue until its empty
+	for qnode := queue.Front(); qnode != nil; qnode = qnode.Next() {
+		queue.Remove(qnode)
 		// iterate through all of its neighbours
 		// mark the visited nodes; enqueue the non-visted
-		for id, node := range qnode.neighbours {
+		for id, node := range qnode.Value.(*node).neighbours {
 			if _, ok := visited[id]; !ok {
 				visited[id] = node
-				queue = append(queue, node)
+				queue.PushBack(node)
 			}
 		}
-		// if no nodes are in the queue break
-		if len(queue) == 0 {
-			break
-		}
 	}
 
-	nodes := make([]Node, 0)
-	// collecte all the nodes into slice
+	nodes := make([]Node, len(visited))
+	// collect all the nodes and return them
 	for _, node := range visited {
 		nodes = append(nodes, node)
 	}