13586005509

Committed 28 Feb 2025 10:14AM UTC coverage: 68.629% (+9.9%) from 58.77%

Build # 13586005509

Build Type

Pull #9521

github

Committed by

web-flow

Commit Message

Merge 37d3a70a5 into 8532955b3

Pull Request Pull Request #9521: unit: remove GOACC, use Go 1.20 native coverage functionality

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96.71

/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 {
                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	// 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.
23	func NewSimpleGraph(g ChannelGraph) (*SimpleGraph, error) {	210✔
24	nodes := make(map[NodeID]int)	210✔
25	adj := make(map[int][]int)	210✔
26	nextIndex := 0	210✔
27		210✔
28	// getNodeIndex returns the integer index of the passed node.	210✔
29	// The returned index is then used to create a simplified adjacency list	210✔
30	// where each node is identified by its index instead of its pubkey, and	210✔
31	// also to create a mapping from node index to node pubkey.	210✔
32	getNodeIndex := func(node Node) int {	7,906✔
33	key := NodeID(node.PubKey())	7,696✔
34	nodeIndex, ok := nodes[key]	7,696✔
35		7,696✔
36	if !ok {	9,568✔
37	nodes[key] = nextIndex	1,872✔
38	nodeIndex = nextIndex	1,872✔
39	nextIndex++	1,872✔
40	}	1,872✔
41
42	return nodeIndex	7,696✔
43	}
44
45	// Iterate over each node and each channel and update the adj and the node
46	// index.
47	err := g.ForEachNode(func(node Node) error {	2,082✔
48	u := getNodeIndex(node)	1,872✔
49		1,872✔
50	return node.ForEachChannel(func(edge ChannelEdge) error {	7,696✔
51	v := getNodeIndex(edge.Peer)	5,824✔
52		5,824✔
53	adj[u] = append(adj[u], v)	5,824✔
54	return nil	5,824✔
55	})	5,824✔
56	})
57	if err != nil {	210✔
58	return nil, err	×
59	}	×
60
61	graph := &SimpleGraph{	210✔
62	Nodes: make([]NodeID, len(nodes)),	210✔
63	Adj: make([][]int, len(nodes)),	210✔
64	}	210✔
65		210✔
66	// Fill the adj and the node index to node pubkey mapping.	210✔
67	for nodeID, nodeIndex := range nodes {	2,082✔
68	graph.Adj[nodeIndex] = adj[nodeIndex]	1,872✔
69	graph.Nodes[nodeIndex] = nodeID	1,872✔
70	}	1,872✔
71
72	// We prepare to give some debug output about the size of the graph.
73	totalChannels := 0	210✔
74	for _, channels := range graph.Adj {	2,082✔
75	totalChannels += len(channels)	1,872✔
76	}	1,872✔
77
78	// The number of channels is double counted, so divide by two.
79	log.Debugf("Initialized simple graph with %d nodes and %d "+	210✔
80	"channels", len(graph.Adj), totalChannels/2)	210✔
81	return graph, nil	210✔
82	}
83
84	// maxVal is a helper function to get the maximal value of all values of a map.
85	func maxVal(mapping map[int]uint32) uint32 {	22✔
86	maxValue := uint32(0)	22✔
87	for _, value := range mapping {	212✔
88	maxValue = max(maxValue, value)	190✔
89	}	190✔
90	return maxValue	22✔
91	}
92
93	// degree determines the number of edges for a node in the graph.
94	func (graph *SimpleGraph) degree(node int) int {	9✔
95	return len(graph.Adj[node])	9✔
96	}	9✔
97
98	// nodeMaxDegree determines the node with the max degree and its degree.
99	func (graph *SimpleGraph) nodeMaxDegree() (int, int) {	1✔
100	var maxNode, maxDegree int	1✔
101	for node := range graph.Adj {	10✔
102	degree := graph.degree(node)	9✔
103	if degree > maxDegree {	11✔
104	maxNode = node	2✔
105	maxDegree = degree	2✔
106	}	2✔
107	}
108	return maxNode, maxDegree	1✔
109	}
110
111	// shortestPathLengths performs a breadth-first-search from a node to all other
112	// nodes, returning the lengths of the paths.
113	func (graph *SimpleGraph) shortestPathLengths(node int) map[int]uint32 {	21✔
114	// level indicates the shell of the search around the root node.	21✔
115	var level uint32	21✔
116	graphOrder := len(graph.Adj)	21✔
117		21✔
118	// nextLevel tracks which nodes should be visited in the next round.	21✔
119	nextLevel := make([]int, 0, graphOrder)	21✔
120		21✔
121	// The root node is put as a starting point for the exploration.	21✔
122	nextLevel = append(nextLevel, node)	21✔
123		21✔
124	// Seen tracks already visited nodes and tracks how far away they are.	21✔
125	seen := make(map[int]uint32, graphOrder)	21✔
126		21✔
127	// Mark the root node as seen.	21✔
128	seen[node] = level	21✔
129		21✔
130	// thisLevel contains the nodes that are explored in the round.	21✔
131	thisLevel := make([]int, 0, graphOrder)	21✔
132		21✔
133	// Abort if we have an empty graph.	21✔
134	if len(graph.Adj) == 0 {	21✔
135	return seen	×
136	}	×
137
138	// We discover other nodes in a ring-like structure as long as we don't
139	// have more nodes to explore.
140	for len(nextLevel) > 0 {	103✔
141	level++	82✔
142		82✔
143	// We swap the queues for efficient memory management.	82✔
144	thisLevel, nextLevel = nextLevel, thisLevel	82✔
145		82✔
146	// Visit all neighboring nodes of the level and mark them as	82✔
147	// seen if they were not discovered before.	82✔
148	for _, thisNode := range thisLevel {	226✔
149	for _, neighbor := range graph.Adj[thisNode] {	608✔
150	_, ok := seen[neighbor]	464✔
151	if !ok {	632✔
152	nextLevel = append(nextLevel, neighbor)	168✔
153	seen[neighbor] = level	168✔
154	}	168✔
155
156	// If we have seen all nodes, we return early.
157	if len(seen) == graphOrder {	485✔
158	return seen	21✔
159	}	21✔
160	}
161	}
162
163	// Empty the queue to be used in the next level.
164	thisLevel = thisLevel[:0:cap(thisLevel)]	61✔
165	}
166
167	return seen	×
168	}
169
170	// nodeEccentricity calculates the eccentricity (longest shortest path to all
171	// other nodes) of a node.
172	func (graph *SimpleGraph) nodeEccentricity(node int) uint32 {	19✔
173	pathLengths := graph.shortestPathLengths(node)	19✔
174	return maxVal(pathLengths)	19✔
175	}	19✔
176
177	// nodeEccentricities calculates the eccentricities for the given nodes.
178	func (graph *SimpleGraph) nodeEccentricities(nodes []int) map[int]uint32 {	3✔
179	eccentricities := make(map[int]uint32, len(graph.Adj))	3✔
180	for _, node := range nodes {	22✔
181	eccentricities[node] = graph.nodeEccentricity(node)	19✔
182	}	19✔
183	return eccentricities	3✔
184	}
185
186	// Diameter returns the maximal eccentricity (longest shortest path
187	// between any node pair) in the graph.
188	//
189	// Note: This method is exact but expensive, use DiameterRadialCutoff instead.
190	func (graph *SimpleGraph) Diameter() uint32 {	1✔
191	nodes := make([]int, len(graph.Adj))	1✔
192	for a := range nodes {	10✔
193	nodes[a] = a	9✔
194	}	9✔
195	eccentricities := graph.nodeEccentricities(nodes)	1✔
196	return maxVal(eccentricities)	1✔
197	}
198
199	// DiameterRadialCutoff is a method to efficiently evaluate the diameter of a
200	// graph. The highest-degree node is usually central in the graph. We can
201	// determine its eccentricity (shortest-longest path length to any other node)
202	// and use it as an approximation for the radius of the network. We then
203	// use this radius to compute a cutoff. All the nodes within a distance of the
204	// cutoff are discarded, as they represent the inside of the graph. We then
205	// loop over all outer nodes and determine their eccentricities, from which we
206	// get the diameter.
207	func (graph *SimpleGraph) DiameterRadialCutoff() uint32 {	1✔
208	// Determine the reference node as the node with the highest degree.	1✔
209	nodeMaxDegree, _ := graph.nodeMaxDegree()	1✔
210		1✔
211	distances := graph.shortestPathLengths(nodeMaxDegree)	1✔
212	eccentricityMaxDegreeNode := maxVal(distances)	1✔
213		1✔
214	// We use the eccentricity to define a cutoff for the interior of the	1✔
215	// graph from the reference node.	1✔
216	cutoff := uint32(float32(eccentricityMaxDegreeNode) * diameterCutoff)	1✔
217	log.Debugf("Cutoff radius is %d hops (max-degree node's "+	1✔
218	"eccentricity is %d)", cutoff, eccentricityMaxDegreeNode)	1✔
219		1✔
220	// Remove the nodes that are close to the reference node.	1✔
221	var nodes []int	1✔
222	for node, distance := range distances {	10✔
223	if distance > cutoff {	10✔
224	nodes = append(nodes, node)	1✔
225	}	1✔
226	}
227	log.Debugf("Evaluated nodes: %d, discarded nodes %d",	1✔
228	len(nodes), len(graph.Adj)-len(nodes))	1✔
229		1✔
230	// Compute the diameter of the remaining nodes.	1✔
231	eccentricities := graph.nodeEccentricities(nodes)	1✔
232	return maxVal(eccentricities)	1✔
233	}

lightningnetwork / lnd / 13586005509

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