topic score cap

score.go

@@ -216,6 +216,11 @@ func (ps *peerScore) score(p peer.ID) float64 {
 		score += topicScore * topicParams.TopicWeight
 	}
 
+	// apply the topic score cap, if any
+	if ps.params.TopicScoreCap > 0 && score > ps.params.TopicScoreCap {
+		score = ps.params.TopicScoreCap
+	}
+
 	// P5: application-specific score
 	p5 := ps.params.AppSpecificScore(p)
 	score += p5 * ps.params.AppSpecificWeight

score_params.go

@@ -45,6 +45,10 @@ type PeerScoreParams struct {
 	// Score parameters per topic.
 	Topics map[string]*TopicScoreParams
 
+	// Aggregate topic score cap; this limits the total contribution of topics towards a positive
+	// score. It must be positive (or 0 for no cap).
+	TopicScoreCap float64
+
 	// P5: Application-specific peer scoring
 	AppSpecificScore  func(p peer.ID) float64
 	AppSpecificWeight float64
@@ -130,6 +134,11 @@ func (p *PeerScoreParams) validate() error {
 		}
 	}
 
+	// check that the topic score is 0 or something positive
+	if p.TopicScoreCap < 0 {
+		return fmt.Errorf("invalid topic score cap; must be positive (or 0 for no cap)")
+	}
+
 	// check that we have an app specific score; the weight can be anything (but expected positive)
 	if p.AppSpecificScore == nil {
 		return fmt.Errorf("missing application specific score function")