f more comments

Author: TheBlueMatt

lightning/src/routing/scoring.rs

@@ -822,21 +822,24 @@ impl<L: Deref<Target = u64>, BRT: Deref<Target = HistoricalBucketRangeTracker>,
 			// sending less than 1/16th of a channel's capacity, or 1/8th if we used the top of the
 			// bucket.
 			let mut total_valid_points_tracked = 0;
-			let decays = self.now.duration_since(*self.last_updated).as_secs()
+			let reqd_decays = self.now.duration_since(*self.last_updated).as_secs()
 				.checked_div(params.historical_no_updates_half_life.as_secs())
 				.map_or(u32::max_value(), |decays| cmp::min(decays, u32::max_value() as u64) as u32);
 			// Rather than actually decaying the individual buckets, which would lose precision, we
-			// simply track whether any buckets have data which wouldn't be decayed to zero, and if
+			// simply track whether all buckets would be decayed to zero, in which case we treat it
+			// as if we had no data.
 			// there are none, treat it as if we had no data.
 			let mut is_fully_decayed = true;
 			for (min_idx, min_bucket) in self.min_liquidity_offset_history.buckets.iter().enumerate() {
-				if min_bucket.checked_shr(decays).unwrap_or(0) > 0 { is_fully_decayed = false; }
+				if min_bucket.checked_shr(reqd_decays).unwrap_or(0) > 0 { is_fully_decayed = false; }
 				for max_bucket in self.max_liquidity_offset_history.buckets.iter().take(8 - min_idx) {
 					total_valid_points_tracked += (*min_bucket as u64) * (*max_bucket as u64);
-					if max_bucket.checked_shr(decays).unwrap_or(0) > 0 { is_fully_decayed = false; }
+					if max_bucket.checked_shr(reqd_decays).unwrap_or(0) > 0 { is_fully_decayed = false; }
 				}
 			}
-			if total_valid_points_tracked.checked_shr(decays).unwrap_or(0) < 31*31 || is_fully_decayed {
+			// If the total valid points is smaller than 1.0 (i.e. 32 in our fixed-point scheme),
+			// treat it as if we were fully decayed.
+			if total_valid_points_tracked.checked_shr(reqd_decays).unwrap_or(0) < 31*31 || is_fully_decayed {
 				// If we don't have any valid points (or, once decayed, we have less than a full
 				// point), redo the non-historical calculation with no liquidity bounds tracked and
 				// the historical penalty multipliers.