129 lines
3.6 KiB
Go
129 lines
3.6 KiB
Go
package autopilot
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import (
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"fmt"
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"github.com/btcsuite/btcutil"
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)
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// WeightedHeuristic is a tuple that associates a weight to an
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// AttachmentHeuristic. This is used to determining a node's final score when
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// querying several heuristics for scores.
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type WeightedHeuristic struct {
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// Weight is this AttachmentHeuristic's relative weight factor. It
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// should be between 0.0 and 1.0.
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Weight float64
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AttachmentHeuristic
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}
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// WeightedCombAttachment is an implementation of the AttachmentHeuristic
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// interface that combines the scores given by several sub-heuristics into one.
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type WeightedCombAttachment struct {
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heuristics []*WeightedHeuristic
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}
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// NewWeightedCombAttachment creates a new instance of a WeightedCombAttachment.
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func NewWeightedCombAttachment(h ...*WeightedHeuristic) (
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AttachmentHeuristic, error) {
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// The sum of weights given to the sub-heuristics must sum to exactly
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// 1.0.
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var sum float64
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for _, w := range h {
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sum += w.Weight
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}
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if sum != 1.0 {
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return nil, fmt.Errorf("weights MUST sum to 1.0 (was %v)", sum)
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}
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return &WeightedCombAttachment{
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heuristics: h,
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}, nil
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}
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// A compile time assertion to ensure WeightedCombAttachment meets the
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// AttachmentHeuristic interface.
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var _ AttachmentHeuristic = (*WeightedCombAttachment)(nil)
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// Name returns the name of this heuristic.
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//
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// NOTE: This is a part of the AttachmentHeuristic interface.
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func (c *WeightedCombAttachment) Name() string {
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return "weightedcomb"
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}
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// NodeScores is a method that given the current channel graph, current set of
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// local channels and funds available, scores the given nodes according to the
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// preference of opening a channel with them. The returned channel candidates
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// maps the NodeID to an attachment directive containing a score and a channel
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// size.
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//
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// The scores is determined by quering the set of sub-heuristics, then
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// combining these scores into a final score according to the active
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// configuration.
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//
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// The returned scores will be in the range [0, 1.0], where 0 indicates no
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// improvement in connectivity if a channel is opened to this node, while 1.0
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// is the maximum possible improvement in connectivity.
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//
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// NOTE: This is a part of the AttachmentHeuristic interface.
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func (c *WeightedCombAttachment) NodeScores(g ChannelGraph, chans []Channel,
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chanSize btcutil.Amount, nodes map[NodeID]struct{}) (
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map[NodeID]*NodeScore, error) {
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// We now query each heuristic to determine the score they give to the
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// nodes for the given channel size.
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var subScores []map[NodeID]*NodeScore
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for _, h := range c.heuristics {
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s, err := h.NodeScores(
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g, chans, chanSize, nodes,
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)
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if err != nil {
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return nil, fmt.Errorf("unable to get sub score: %v",
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err)
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}
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subScores = append(subScores, s)
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}
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// We combine the scores given by the sub-heuristics by using the
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// heruistics' given weight factor.
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scores := make(map[NodeID]*NodeScore)
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for nID := range nodes {
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score := &NodeScore{
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NodeID: nID,
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}
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// Each sub-heuristic should have scored the node, if not it is
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// implicitly given a zero score by that heuristic.
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for i, h := range c.heuristics {
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sub, ok := subScores[i][nID]
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if !ok {
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continue
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}
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// Use the heuristic's weight factor to determine of
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// how much weight we should give to this particular
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// score.
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score.Score += h.Weight * sub.Score
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}
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switch {
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// Instead of adding a node with score 0 to the returned set,
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// we just skip it.
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case score.Score == 0:
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continue
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// Sanity check the new score.
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case score.Score < 0 || score.Score > 1.0:
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return nil, fmt.Errorf("Invalid node score from "+
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"combination: %v", score.Score)
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}
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scores[nID] = score
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}
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return scores, nil
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}
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