64 lines
1.6 KiB
Go
64 lines
1.6 KiB
Go
package ctxmgr
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import (
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"math"
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"time"
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)
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// CalculateDecayedWeight 计算考虑时间半衰期与里程碑豁免后的有效权重
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func CalculateDecayedWeight(rawWeight float64, createdAt time.Time, isMilestone bool, cfg TimeDecayConfig) float64 {
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if rawWeight <= 0 {
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rawWeight = 1.00
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}
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if !cfg.Enabled {
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return rawWeight
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}
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// 里程碑事件豁免衰减，作为永久基石
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if isMilestone && cfg.MilestoneExempt {
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return rawWeight
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}
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halfLife := cfg.HalfLifeDays
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if halfLife <= 0 {
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halfLife = 7.0
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}
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daysDiff := time.Since(createdAt).Hours() / 24.0
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if daysDiff <= 0 {
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return rawWeight
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}
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lambda := math.Ln2 / halfLife
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decayFactor := math.Exp(-lambda * daysDiff)
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decayed := rawWeight * decayFactor
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// 应用衰减下限保护，防止早期有价值信息完全被截断
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floor := rawWeight * cfg.MinWeightFloor
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if decayed < floor {
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decayed = floor
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}
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return math.Round(decayed*1000) / 1000
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}
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// ApplyTimeDecayToActivities 对活动流批量应用时间衰减并按最终有效权重重排
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func ApplyTimeDecayToActivities(items []ActivityItem, cfg TimeDecayConfig) []ActivityItem {
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res := make([]ActivityItem, len(items))
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for i, it := range items {
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it.DecayedWeight = CalculateDecayedWeight(it.RawWeight, it.CreatedAt, it.IsMilestone, cfg)
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res[i] = it
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}
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// 稳定排序：按 DecayedWeight 降序，相同时按时间倒序
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for i := 0; i < len(res); i++ {
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for j := i + 1; j < len(res); j++ {
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if res[j].DecayedWeight > res[i].DecayedWeight ||
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(res[j].DecayedWeight == res[i].DecayedWeight && res[j].CreatedAt.After(res[i].CreatedAt)) {
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res[i], res[j] = res[j], res[i]
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}
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}
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}
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return res
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}
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