bvandeusen
8c3d06c0a1
Composes Score over a candidate slice, sorts descending, truncates. Pure — no IO. Liked-rank-higher and high-skip-ranks-last behaviors are stable across RNG seeds (jitter band is smaller than LikeBoost and SkipPenalty).
49 lines
1.0 KiB
Go
49 lines
1.0 KiB
Go
package recommendation
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import (
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"sort"
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"time"
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"git.fabledsword.com/bvandeusen/minstrel/internal/db/dbq"
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)
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// Candidate pairs a track with the inputs needed to score it.
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type Candidate struct {
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Track dbq.Track
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Inputs ScoringInputs
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}
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// Shuffle scores each candidate, sorts descending by score, and returns
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// the top `limit` candidates. limit <= 0 returns nil; nil input returns
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// nil. Pure — no IO, no global state beyond the rng callback.
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func Shuffle(
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candidates []Candidate,
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weights ScoringWeights,
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now time.Time,
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rng func() float64,
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limit int,
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) []Candidate {
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if len(candidates) == 0 || limit <= 0 {
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return nil
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}
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scored := make([]struct {
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c Candidate
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score float64
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}, len(candidates))
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for i, c := range candidates {
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scored[i].c = c
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scored[i].score = Score(c.Inputs, weights, now, rng)
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}
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sort.Slice(scored, func(i, j int) bool {
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return scored[i].score > scored[j].score
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})
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if limit > len(scored) {
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limit = len(scored)
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}
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out := make([]Candidate, limit)
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for i := 0; i < limit; i++ {
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out[i] = scored[i].c
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}
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return out
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}
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