13423774416

Committed 19 Feb 2025 10:39PM UTC coverage: 49.338% (-9.5%) from 58.794%

Build # 13423774416

Build Type

Pull #9484

github

Committed by

Abdulkbk

Commit Message

lnutils: add createdir util function

This utility function replaces repetitive logic patterns
throughout LND.

Pull Request Pull Request #9484: lnutils: add createDir util function

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/autopilot/simple_graph.go

package autopilot

// diameterCutoff is used to discard nodes in the diameter calculation.
// It is the multiplier for the eccentricity of the highest-degree node,
// serving as a cutoff to discard all nodes with a smaller hop distance. This
// number should not be set close to 1 and is a tradeoff for computation cost,
// where 0 is maximally costly.
const diameterCutoff = 0.75

// SimpleGraph stores a simplified adj graph of a channel graph to speed
// up graph processing by eliminating all unnecessary hashing and map access.
type SimpleGraph struct {
        // Nodes is a map from node index to NodeID.
        Nodes []NodeID

        // Adj stores nodes and neighbors in an adjacency list.
        Adj [][]int
}

// NewSimpleGraph creates a simplified graph from the current channel graph.
// Returns an error if the channel graph iteration fails due to underlying
// failure.
func NewSimpleGraph(g ChannelGraph) (*SimpleGraph, error) {
        nodes := make(map[NodeID]int)
        adj := make(map[int][]int)
        nextIndex := 0

        // getNodeIndex returns the integer index of the passed node.
        // The returned index is then used to create a simplified adjacency list
        // where each node is identified by its index instead of its pubkey, and
        // also to create a mapping from node index to node pubkey.
        getNodeIndex := func(node Node) int {
                key := NodeID(node.PubKey())
                nodeIndex, ok := nodes[key]

                if !ok {
                        nodes[key] = nextIndex
                        nodeIndex = nextIndex
                        nextIndex++
                }

                return nodeIndex
        }

        // Iterate over each node and each channel and update the adj and the node
        // index.
        err := g.ForEachNode(func(node Node) error {
                u := getNodeIndex(node)

                return node.ForEachChannel(func(edge ChannelEdge) error {
                        v := getNodeIndex(edge.Peer)

                        adj[u] = append(adj[u], v)
                        return nil
                })
        })
        if err != nil {
                return nil, err
        }

        graph := &SimpleGraph{
                Nodes: make([]NodeID, len(nodes)),
                Adj:   make([][]int, len(nodes)),
        }

        // Fill the adj and the node index to node pubkey mapping.
        for nodeID, nodeIndex := range nodes {
                graph.Adj[nodeIndex] = adj[nodeIndex]
                graph.Nodes[nodeIndex] = nodeID
        }

        // We prepare to give some debug output about the size of the graph.
        totalChannels := 0
        for _, channels := range graph.Adj {
                totalChannels += len(channels)
        }

        // The number of channels is double counted, so divide by two.
        log.Debugf("Initialized simple graph with %d nodes and %d "+
                "channels", len(graph.Adj), totalChannels/2)
        return graph, nil
}

// maxVal is a helper function to get the maximal value of all values of a map.
func maxVal(mapping map[int]uint32) uint32 {
        maxValue := uint32(0)
        for _, value := range mapping {
                if maxValue < value {
                        maxValue = value
                }
        }
        return maxValue
}

// degree determines the number of edges for a node in the graph.
func (graph *SimpleGraph) degree(node int) int {
        return len(graph.Adj[node])
}

// nodeMaxDegree determines the node with the max degree and its degree.
func (graph *SimpleGraph) nodeMaxDegree() (int, int) {
        var maxNode, maxDegree int
        for node := range graph.Adj {
                degree := graph.degree(node)
                if degree > maxDegree {
                        maxNode = node
                        maxDegree = degree
                }
        }
        return maxNode, maxDegree
}

// shortestPathLengths performs a breadth-first-search from a node to all other
// nodes, returning the lengths of the paths.
func (graph *SimpleGraph) shortestPathLengths(node int) map[int]uint32 {
        // level indicates the shell of the search around the root node.
        var level uint32
        graphOrder := len(graph.Adj)

        // nextLevel tracks which nodes should be visited in the next round.
        nextLevel := make([]int, 0, graphOrder)

        // The root node is put as a starting point for the exploration.
        nextLevel = append(nextLevel, node)

        // Seen tracks already visited nodes and tracks how far away they are.
        seen := make(map[int]uint32, graphOrder)

        // Mark the root node as seen.
        seen[node] = level

        // thisLevel contains the nodes that are explored in the round.
        thisLevel := make([]int, 0, graphOrder)

        // Abort if we have an empty graph.
        if len(graph.Adj) == 0 {
                return seen
        }

        // We discover other nodes in a ring-like structure as long as we don't
        // have more nodes to explore.
        for len(nextLevel) > 0 {
                level++

                // We swap the queues for efficient memory management.
                thisLevel, nextLevel = nextLevel, thisLevel

                // Visit all neighboring nodes of the level and mark them as
                // seen if they were not discovered before.
                for _, thisNode := range thisLevel {
                        for _, neighbor := range graph.Adj[thisNode] {
                                _, ok := seen[neighbor]
                                if !ok {
                                        nextLevel = append(nextLevel, neighbor)
                                        seen[neighbor] = level
                                }

                                // If we have seen all nodes, we return early.
                                if len(seen) == graphOrder {
                                        return seen
                                }
                        }
                }

                // Empty the queue to be used in the next level.
                thisLevel = thisLevel[:0:cap(thisLevel)]
        }

        return seen
}

// nodeEccentricity calculates the eccentricity (longest shortest path to all
// other nodes) of a node.
func (graph *SimpleGraph) nodeEccentricity(node int) uint32 {
        pathLengths := graph.shortestPathLengths(node)
        return maxVal(pathLengths)
}

// nodeEccentricities calculates the eccentricities for the given nodes.
func (graph *SimpleGraph) nodeEccentricities(nodes []int) map[int]uint32 {
        eccentricities := make(map[int]uint32, len(graph.Adj))
        for _, node := range nodes {
                eccentricities[node] = graph.nodeEccentricity(node)
        }
        return eccentricities
}

// Diameter returns the maximal eccentricity (longest shortest path
// between any node pair) in the graph.
//
// Note: This method is exact but expensive, use DiameterRadialCutoff instead.
func (graph *SimpleGraph) Diameter() uint32 {
        nodes := make([]int, len(graph.Adj))
        for a := range nodes {
                nodes[a] = a
        }
        eccentricities := graph.nodeEccentricities(nodes)
        return maxVal(eccentricities)
}

// DiameterRadialCutoff is a method to efficiently evaluate the diameter of a
// graph. The highest-degree node is usually central in the graph. We can
// determine its eccentricity (shortest-longest path length to any other node)
// and use it as an approximation for the radius of the network. We then
// use this radius to compute a cutoff. All the nodes within a distance of the
// cutoff are discarded, as they represent the inside of the graph. We then
// loop over all outer nodes and determine their eccentricities, from which we
// get the diameter.
func (graph *SimpleGraph) DiameterRadialCutoff() uint32 {
        // Determine the reference node as the node with the highest degree.
        nodeMaxDegree, _ := graph.nodeMaxDegree()

        distances := graph.shortestPathLengths(nodeMaxDegree)
        eccentricityMaxDegreeNode := maxVal(distances)

        // We use the eccentricity to define a cutoff for the interior of the
        // graph from the reference node.
        cutoff := uint32(float32(eccentricityMaxDegreeNode) * diameterCutoff)
        log.Debugf("Cutoff radius is %d hops (max-degree node's "+
                "eccentricity is %d)", cutoff, eccentricityMaxDegreeNode)

        // Remove the nodes that are close to the reference node.
        var nodes []int
        for node, distance := range distances {
                if distance > cutoff {
                        nodes = append(nodes, node)
                }
        }
        log.Debugf("Evaluated nodes: %d, discarded nodes %d",
                len(nodes), len(graph.Adj)-len(nodes))

        // Compute the diameter of the remaining nodes.
        eccentricities := graph.nodeEccentricities(nodes)
        return maxVal(eccentricities)
}

1	package autopilot
2
3	// diameterCutoff is used to discard nodes in the diameter calculation.
4	// It is the multiplier for the eccentricity of the highest-degree node,
5	// serving as a cutoff to discard all nodes with a smaller hop distance. This
6	// number should not be set close to 1 and is a tradeoff for computation cost,
7	// where 0 is maximally costly.
8	const diameterCutoff = 0.75
9
10	// SimpleGraph stores a simplified adj graph of a channel graph to speed
11	// up graph processing by eliminating all unnecessary hashing and map access.
12	type SimpleGraph struct {
13	// Nodes is a map from node index to NodeID.
14	Nodes []NodeID
15
16	// Adj stores nodes and neighbors in an adjacency list.
17	Adj [][]int
18	}
19
20	// NewSimpleGraph creates a simplified graph from the current channel graph.
21	// Returns an error if the channel graph iteration fails due to underlying
22	// failure.
UNCOV 23	func NewSimpleGraph(g ChannelGraph) (*SimpleGraph, error) {	×
UNCOV 24	nodes := make(map[NodeID]int)	×
UNCOV 25	adj := make(map[int][]int)	×
UNCOV 26	nextIndex := 0	×
UNCOV 27		×
UNCOV 28	// getNodeIndex returns the integer index of the passed node.	×
UNCOV 29	// The returned index is then used to create a simplified adjacency list	×
UNCOV 30	// where each node is identified by its index instead of its pubkey, and	×
UNCOV 31	// also to create a mapping from node index to node pubkey.	×
UNCOV 32	getNodeIndex := func(node Node) int {	×
UNCOV 33	key := NodeID(node.PubKey())	×
UNCOV 34	nodeIndex, ok := nodes[key]	×
UNCOV 35		×
UNCOV 36	if !ok {	×
UNCOV 37	nodes[key] = nextIndex	×
UNCOV 38	nodeIndex = nextIndex	×
UNCOV 39	nextIndex++	×
UNCOV 40	}	×
41
UNCOV 42	return nodeIndex	×
43	}
44
45	// Iterate over each node and each channel and update the adj and the node
46	// index.
UNCOV 47	err := g.ForEachNode(func(node Node) error {	×
UNCOV 48	u := getNodeIndex(node)	×
UNCOV 49		×
UNCOV 50	return node.ForEachChannel(func(edge ChannelEdge) error {	×
UNCOV 51	v := getNodeIndex(edge.Peer)	×
UNCOV 52		×
UNCOV 53	adj[u] = append(adj[u], v)	×
UNCOV 54	return nil	×
UNCOV 55	})	×
56	})
UNCOV 57	if err != nil {	×
58	return nil, err	×
59	}	×
60
UNCOV 61	graph := &SimpleGraph{	×
UNCOV 62	Nodes: make([]NodeID, len(nodes)),	×
UNCOV 63	Adj: make([][]int, len(nodes)),	×
UNCOV 64	}	×
UNCOV 65		×
UNCOV 66	// Fill the adj and the node index to node pubkey mapping.	×
UNCOV 67	for nodeID, nodeIndex := range nodes {	×
UNCOV 68	graph.Adj[nodeIndex] = adj[nodeIndex]	×
UNCOV 69	graph.Nodes[nodeIndex] = nodeID	×
UNCOV 70	}	×
71
72	// We prepare to give some debug output about the size of the graph.
UNCOV 73	totalChannels := 0	×
UNCOV 74	for _, channels := range graph.Adj {	×
UNCOV 75	totalChannels += len(channels)	×
UNCOV 76	}	×
77
78	// The number of channels is double counted, so divide by two.
UNCOV 79	log.Debugf("Initialized simple graph with %d nodes and %d "+	×
UNCOV 80	"channels", len(graph.Adj), totalChannels/2)	×
UNCOV 81	return graph, nil	×
82	}
83
84	// maxVal is a helper function to get the maximal value of all values of a map.
UNCOV 85	func maxVal(mapping map[int]uint32) uint32 {	×
UNCOV 86	maxValue := uint32(0)	×
UNCOV 87	for _, value := range mapping {	×
UNCOV 88	if maxValue < value {	×
UNCOV 89	maxValue = value	×
UNCOV 90	}	×
91	}
92	return maxValue
93	}
UNCOV 94		×
UNCOV 95	// degree determines the number of edges for a node in the graph.	×
UNCOV 96	func (graph *SimpleGraph) degree(node int) int {	×
97	return len(graph.Adj[node])
98	}
UNCOV 99		×
UNCOV 100	// nodeMaxDegree determines the node with the max degree and its degree.	×
UNCOV 101	func (graph *SimpleGraph) nodeMaxDegree() (int, int) {	×
UNCOV 102	var maxNode, maxDegree int	×
UNCOV 103	for node := range graph.Adj {	×
UNCOV 104	degree := graph.degree(node)	×
UNCOV 105	if degree > maxDegree {	×
UNCOV 106	maxNode = node	×
107	maxDegree = degree
UNCOV 108	}	×
109	}
110	return maxNode, maxDegree
111	}
112
UNCOV 113	// shortestPathLengths performs a breadth-first-search from a node to all other	×
UNCOV 114	// nodes, returning the lengths of the paths.	×
UNCOV 115	func (graph *SimpleGraph) shortestPathLengths(node int) map[int]uint32 {	×
UNCOV 116	// level indicates the shell of the search around the root node.	×
UNCOV 117	var level uint32	×
UNCOV 118	graphOrder := len(graph.Adj)	×
UNCOV 119		×
UNCOV 120	// nextLevel tracks which nodes should be visited in the next round.	×
UNCOV 121	nextLevel := make([]int, 0, graphOrder)	×
UNCOV 122		×
UNCOV 123	// The root node is put as a starting point for the exploration.	×
UNCOV 124	nextLevel = append(nextLevel, node)	×
UNCOV 125		×
UNCOV 126	// Seen tracks already visited nodes and tracks how far away they are.	×
UNCOV 127	seen := make(map[int]uint32, graphOrder)	×
UNCOV 128		×
UNCOV 129	// Mark the root node as seen.	×
UNCOV 130	seen[node] = level	×
UNCOV 131		×
UNCOV 132	// thisLevel contains the nodes that are explored in the round.	×
UNCOV 133	thisLevel := make([]int, 0, graphOrder)	×
UNCOV 134		×
135	// Abort if we have an empty graph.	×
136	if len(graph.Adj) == 0 {	×
137	return seen
138	}
139
UNCOV 140	// We discover other nodes in a ring-like structure as long as we don't	×
UNCOV 141	// have more nodes to explore.	×
UNCOV 142	for len(nextLevel) > 0 {	×
UNCOV 143	level++	×
UNCOV 144		×
UNCOV 145	// We swap the queues for efficient memory management.	×
UNCOV 146	thisLevel, nextLevel = nextLevel, thisLevel	×
UNCOV 147		×
UNCOV 148	// Visit all neighboring nodes of the level and mark them as	×
UNCOV 149	// seen if they were not discovered before.	×
UNCOV 150	for _, thisNode := range thisLevel {	×
UNCOV 151	for _, neighbor := range graph.Adj[thisNode] {	×
UNCOV 152	_, ok := seen[neighbor]	×
UNCOV 153	if !ok {	×
UNCOV 154	nextLevel = append(nextLevel, neighbor)	×
155	seen[neighbor] = level
156	}
UNCOV 157		×
UNCOV 158	// If we have seen all nodes, we return early.	×
UNCOV 159	if len(seen) == graphOrder {	×
160	return seen
161	}
162	}
163	}
UNCOV 164		×
165	// Empty the queue to be used in the next level.
166	thisLevel = thisLevel[:0:cap(thisLevel)]
167	}	×
168
169	return seen
170	}
171
UNCOV 172	// nodeEccentricity calculates the eccentricity (longest shortest path to all	×
UNCOV 173	// other nodes) of a node.	×
UNCOV 174	func (graph *SimpleGraph) nodeEccentricity(node int) uint32 {	×
UNCOV 175	pathLengths := graph.shortestPathLengths(node)	×
176	return maxVal(pathLengths)
177	}
UNCOV 178		×
UNCOV 179	// nodeEccentricities calculates the eccentricities for the given nodes.	×
UNCOV 180	func (graph *SimpleGraph) nodeEccentricities(nodes []int) map[int]uint32 {	×
UNCOV 181	eccentricities := make(map[int]uint32, len(graph.Adj))	×
UNCOV 182	for _, node := range nodes {	×
UNCOV 183	eccentricities[node] = graph.nodeEccentricity(node)	×
184	}
185	return eccentricities
186	}
187
188	// Diameter returns the maximal eccentricity (longest shortest path
189	// between any node pair) in the graph.
UNCOV 190	//	×
UNCOV 191	// Note: This method is exact but expensive, use DiameterRadialCutoff instead.	×
UNCOV 192	func (graph *SimpleGraph) Diameter() uint32 {	×
UNCOV 193	nodes := make([]int, len(graph.Adj))	×
UNCOV 194	for a := range nodes {	×
UNCOV 195	nodes[a] = a	×
UNCOV 196	}	×
197	eccentricities := graph.nodeEccentricities(nodes)
198	return maxVal(eccentricities)
199	}
200
201	// DiameterRadialCutoff is a method to efficiently evaluate the diameter of a
202	// graph. The highest-degree node is usually central in the graph. We can
203	// determine its eccentricity (shortest-longest path length to any other node)
204	// and use it as an approximation for the radius of the network. We then
205	// use this radius to compute a cutoff. All the nodes within a distance of the
206	// cutoff are discarded, as they represent the inside of the graph. We then
UNCOV 207	// loop over all outer nodes and determine their eccentricities, from which we	×
UNCOV 208	// get the diameter.	×
UNCOV 209	func (graph *SimpleGraph) DiameterRadialCutoff() uint32 {	×
UNCOV 210	// Determine the reference node as the node with the highest degree.	×
UNCOV 211	nodeMaxDegree, _ := graph.nodeMaxDegree()	×
UNCOV 212		×
UNCOV 213	distances := graph.shortestPathLengths(nodeMaxDegree)	×
UNCOV 214	eccentricityMaxDegreeNode := maxVal(distances)	×
UNCOV 215		×
UNCOV 216	// We use the eccentricity to define a cutoff for the interior of the	×
UNCOV 217	// graph from the reference node.	×
UNCOV 218	cutoff := uint32(float32(eccentricityMaxDegreeNode) * diameterCutoff)	×
UNCOV 219	log.Debugf("Cutoff radius is %d hops (max-degree node's "+	×
UNCOV 220	"eccentricity is %d)", cutoff, eccentricityMaxDegreeNode)	×
UNCOV 221		×
UNCOV 222	// Remove the nodes that are close to the reference node.	×
UNCOV 223	var nodes []int	×
UNCOV 224	for node, distance := range distances {	×
UNCOV 225	if distance > cutoff {	×
226	nodes = append(nodes, node)
UNCOV 227	}	×
UNCOV 228	}	×
UNCOV 229	log.Debugf("Evaluated nodes: %d, discarded nodes %d",	×
UNCOV 230	len(nodes), len(graph.Adj)-len(nodes))	×
UNCOV 231		×
UNCOV 232	// Compute the diameter of the remaining nodes.	×
233	eccentricities := graph.nodeEccentricities(nodes)
234	return maxVal(eccentricities)
235	}

lightningnetwork / lnd / 13423774416

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