15426258570

Committed 03 Jun 2025 07:36PM UTC coverage: 58.587%. First build

Build # 15426258570

Build Type

Pull #9893

github

Committed by

web-flow

Commit Message

Merge 4f69df485 into c52a6ddeb

Pull Request Pull Request #9893: fix memory leak cherry pick

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/autopilot/simple_graph.go

package autopilot

import "context"

// 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(ctx context.Context, 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(ctx, func(ctx context.Context, node Node) error {
                u := getNodeIndex(node)

                return node.ForEachChannel(
                        ctx, func(_ context.Context,
                                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 {
                maxValue = max(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	import "context"
4
5	// diameterCutoff is used to discard nodes in the diameter calculation.
6	// It is the multiplier for the eccentricity of the highest-degree node,
7	// serving as a cutoff to discard all nodes with a smaller hop distance. This
8	// number should not be set close to 1 and is a tradeoff for computation cost,
9	// where 0 is maximally costly.
10	const diameterCutoff = 0.75
11
12	// SimpleGraph stores a simplified adj graph of a channel graph to speed
13	// up graph processing by eliminating all unnecessary hashing and map access.
14	type SimpleGraph struct {
15	// Nodes is a map from node index to NodeID.
16	Nodes []NodeID
17
18	// Adj stores nodes and neighbors in an adjacency list.
19	Adj [][]int
20	}
21
22	// NewSimpleGraph creates a simplified graph from the current channel graph.
23	// Returns an error if the channel graph iteration fails due to underlying
24	// failure.
NEW 25	func NewSimpleGraph(ctx context.Context, g ChannelGraph) (*SimpleGraph, error) {	×
26	nodes := make(map[NodeID]int)	×
27	adj := make(map[int][]int)	×
28	nextIndex := 0	×
29		×
30	// getNodeIndex returns the integer index of the passed node.	×
31	// The returned index is then used to create a simplified adjacency list	×
32	// where each node is identified by its index instead of its pubkey, and	×
33	// also to create a mapping from node index to node pubkey.	×
34	getNodeIndex := func(node Node) int {	×
35	key := NodeID(node.PubKey())	×
36	nodeIndex, ok := nodes[key]	×
37		×
38	if !ok {	×
39	nodes[key] = nextIndex	×
40	nodeIndex = nextIndex	×
41	nextIndex++	×
42	}	×
43
44	return nodeIndex	×
45	}
46
47	// Iterate over each node and each channel and update the adj and the
48	// node index.
NEW 49	err := g.ForEachNode(ctx, func(ctx context.Context, node Node) error {	×
50	u := getNodeIndex(node)	×
51		×
NEW 52	return node.ForEachChannel(	×
NEW 53	ctx, func(_ context.Context,	×
NEW 54	edge ChannelEdge) error {	×
NEW 55		×
NEW 56	v := getNodeIndex(edge.Peer)	×
NEW 57		×
NEW 58	adj[u] = append(adj[u], v)	×
59		×
NEW 60	return nil	×
NEW 61	},	×
62	)
63	})
64	if err != nil {	×
65	return nil, err	×
66	}	×
67
68	graph := &SimpleGraph{	×
69	Nodes: make([]NodeID, len(nodes)),	×
70	Adj: make([][]int, len(nodes)),	×
71	}	×
72		×
73	// Fill the adj and the node index to node pubkey mapping.	×
74	for nodeID, nodeIndex := range nodes {	×
75	graph.Adj[nodeIndex] = adj[nodeIndex]	×
76	graph.Nodes[nodeIndex] = nodeID	×
77	}	×
78
79	// We prepare to give some debug output about the size of the graph.
80	totalChannels := 0	×
81	for _, channels := range graph.Adj {	×
82	totalChannels += len(channels)	×
83	}	×
84
85	// The number of channels is double counted, so divide by two.
86	log.Debugf("Initialized simple graph with %d nodes and %d "+	×
87	"channels", len(graph.Adj), totalChannels/2)	×
88	return graph, nil	×
89	}
90
91	// maxVal is a helper function to get the maximal value of all values of a map.
92	func maxVal(mapping map[int]uint32) uint32 {	×
93	maxValue := uint32(0)	×
94	for _, value := range mapping {	×
95	maxValue = max(maxValue, value)	×
96	}	×
97	return maxValue	×
98	}
99
100	// degree determines the number of edges for a node in the graph.
101	func (graph *SimpleGraph) degree(node int) int {	×
102	return len(graph.Adj[node])	×
103	}	×
104
105	// nodeMaxDegree determines the node with the max degree and its degree.
106	func (graph *SimpleGraph) nodeMaxDegree() (int, int) {	×
107	var maxNode, maxDegree int	×
108	for node := range graph.Adj {	×
109	degree := graph.degree(node)	×
110	if degree > maxDegree {	×
111	maxNode = node	×
112	maxDegree = degree	×
113	}	×
114	}
115	return maxNode, maxDegree	×
116	}
117
118	// shortestPathLengths performs a breadth-first-search from a node to all other
119	// nodes, returning the lengths of the paths.
120	func (graph *SimpleGraph) shortestPathLengths(node int) map[int]uint32 {	×
121	// level indicates the shell of the search around the root node.	×
122	var level uint32	×
123	graphOrder := len(graph.Adj)	×
124		×
125	// nextLevel tracks which nodes should be visited in the next round.	×
126	nextLevel := make([]int, 0, graphOrder)	×
127		×
128	// The root node is put as a starting point for the exploration.	×
129	nextLevel = append(nextLevel, node)	×
130		×
131	// Seen tracks already visited nodes and tracks how far away they are.	×
132	seen := make(map[int]uint32, graphOrder)	×
133		×
134	// Mark the root node as seen.	×
135	seen[node] = level	×
136		×
137	// thisLevel contains the nodes that are explored in the round.	×
138	thisLevel := make([]int, 0, graphOrder)	×
139		×
140	// Abort if we have an empty graph.	×
141	if len(graph.Adj) == 0 {	×
142	return seen	×
143	}	×
144
145	// We discover other nodes in a ring-like structure as long as we don't
146	// have more nodes to explore.
147	for len(nextLevel) > 0 {	×
148	level++	×
149		×
150	// We swap the queues for efficient memory management.	×
151	thisLevel, nextLevel = nextLevel, thisLevel	×
152		×
153	// Visit all neighboring nodes of the level and mark them as	×
154	// seen if they were not discovered before.	×
155	for _, thisNode := range thisLevel {	×
156	for _, neighbor := range graph.Adj[thisNode] {	×
157	_, ok := seen[neighbor]	×
158	if !ok {	×
159	nextLevel = append(nextLevel, neighbor)	×
160	seen[neighbor] = level	×
161	}	×
162
163	// If we have seen all nodes, we return early.
164	if len(seen) == graphOrder {	×
165	return seen	×
166	}	×
167	}
168	}
169
170	// Empty the queue to be used in the next level.
171	thisLevel = thisLevel[:0:cap(thisLevel)]	×
172	}
173
174	return seen	×
175	}
176
177	// nodeEccentricity calculates the eccentricity (longest shortest path to all
178	// other nodes) of a node.
179	func (graph *SimpleGraph) nodeEccentricity(node int) uint32 {	×
180	pathLengths := graph.shortestPathLengths(node)	×
181	return maxVal(pathLengths)	×
182	}	×
183
184	// nodeEccentricities calculates the eccentricities for the given nodes.
185	func (graph *SimpleGraph) nodeEccentricities(nodes []int) map[int]uint32 {	×
186	eccentricities := make(map[int]uint32, len(graph.Adj))	×
187	for _, node := range nodes {	×
188	eccentricities[node] = graph.nodeEccentricity(node)	×
189	}	×
190	return eccentricities	×
191	}
192
193	// Diameter returns the maximal eccentricity (longest shortest path
194	// between any node pair) in the graph.
195	//
196	// Note: This method is exact but expensive, use DiameterRadialCutoff instead.
197	func (graph *SimpleGraph) Diameter() uint32 {	×
198	nodes := make([]int, len(graph.Adj))	×
199	for a := range nodes {	×
200	nodes[a] = a	×
201	}	×
202	eccentricities := graph.nodeEccentricities(nodes)	×
203	return maxVal(eccentricities)	×
204	}
205
206	// DiameterRadialCutoff is a method to efficiently evaluate the diameter of a
207	// graph. The highest-degree node is usually central in the graph. We can
208	// determine its eccentricity (shortest-longest path length to any other node)
209	// and use it as an approximation for the radius of the network. We then
210	// use this radius to compute a cutoff. All the nodes within a distance of the
211	// cutoff are discarded, as they represent the inside of the graph. We then
212	// loop over all outer nodes and determine their eccentricities, from which we
213	// get the diameter.
214	func (graph *SimpleGraph) DiameterRadialCutoff() uint32 {	×
215	// Determine the reference node as the node with the highest degree.	×
216	nodeMaxDegree, _ := graph.nodeMaxDegree()	×
217		×
218	distances := graph.shortestPathLengths(nodeMaxDegree)	×
219	eccentricityMaxDegreeNode := maxVal(distances)	×
220		×
221	// We use the eccentricity to define a cutoff for the interior of the	×
222	// graph from the reference node.	×
223	cutoff := uint32(float32(eccentricityMaxDegreeNode) * diameterCutoff)	×
224	log.Debugf("Cutoff radius is %d hops (max-degree node's "+	×
225	"eccentricity is %d)", cutoff, eccentricityMaxDegreeNode)	×
226		×
227	// Remove the nodes that are close to the reference node.	×
228	var nodes []int	×
229	for node, distance := range distances {	×
230	if distance > cutoff {	×
231	nodes = append(nodes, node)	×
232	}	×
233	}
234	log.Debugf("Evaluated nodes: %d, discarded nodes %d",	×
235	len(nodes), len(graph.Adj)-len(nodes))	×
236		×
237	// Compute the diameter of the remaining nodes.	×
238	eccentricities := graph.nodeEccentricities(nodes)	×
239	return maxVal(eccentricities)	×
240	}

lightningnetwork / lnd / 15426258570

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