67 lines
1.7 KiB
Go
67 lines
1.7 KiB
Go
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package autopilot
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// SimpleGraph stores a simplifed adj graph of a channel graph to speed
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// up graph processing by eliminating all unnecessary hashing and map access.
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type SimpleGraph struct {
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// Nodes is a map from node index to NodeID.
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Nodes []NodeID
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// Adj stores nodes and neighbors in an adjacency list.
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Adj [][]int
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}
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// NewSimpleGraph creates a simplified graph from the current channel graph.
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// Returns an error if the channel graph iteration fails due to underlying
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// failure.
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func NewSimpleGraph(g ChannelGraph) (*SimpleGraph, error) {
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nodes := make(map[NodeID]int)
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adj := make(map[int][]int)
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nextIndex := 0
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// getNodeIndex returns the integer index of the passed node.
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// The returned index is then used to create a simplifed adjacency list
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// where each node is identified by its index instead of its pubkey, and
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// also to create a mapping from node index to node pubkey.
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getNodeIndex := func(node Node) int {
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key := NodeID(node.PubKey())
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nodeIndex, ok := nodes[key]
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if !ok {
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nodes[key] = nextIndex
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nodeIndex = nextIndex
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nextIndex++
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}
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return nodeIndex
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}
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// Iterate over each node and each channel and update the adj and the node
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// index.
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err := g.ForEachNode(func(node Node) error {
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u := getNodeIndex(node)
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return node.ForEachChannel(func(edge ChannelEdge) error {
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v := getNodeIndex(edge.Peer)
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adj[u] = append(adj[u], v)
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return nil
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})
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})
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if err != nil {
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return nil, err
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}
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graph := &SimpleGraph{
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Nodes: make([]NodeID, len(nodes)),
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Adj: make([][]int, len(nodes)),
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}
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// Fill the adj and the node index to node pubkey mapping.
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for nodeID, nodeIndex := range nodes {
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graph.Adj[nodeIndex] = adj[nodeIndex]
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graph.Nodes[nodeIndex] = nodeID
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}
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return graph, nil
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}
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