f add comments

Author: TheBlueMatt

lightning/src/routing/scoring.rs

@@ -1864,6 +1864,9 @@ mod bucketed_history {
 			let mut total_valid_points_tracked = 0;
 			for (min_idx, min_bucket) in self.min_liquidity_offset_history.buckets.iter().enumerate() {
 				for max_bucket in self.max_liquidity_offset_history.buckets.iter().take(32 - min_idx) {
+					// In testing, raising the weights of buckets to a high power led to better
+					// scoring results. Thus, we raise the bucket weights to the 4th power here (by
+					// squaring the result of multiplying the weights).
 					let mut bucket_weight = (*min_bucket as u64) * (*max_bucket as u64);
 					bucket_weight *= bucket_weight;
 					total_valid_points_tracked += bucket_weight;
@@ -1992,6 +1995,10 @@ mod bucketed_history {
 					if *max_bucket != 0 {
 						highest_max_bucket_with_points = cmp::max(highest_max_bucket_with_points, max_idx);
 					}
+					// In testing, raising the weights of buckets to a high power led to better
+					// scoring results. Thus, we raise the bucket weights to the 4th power here (by
+					// squaring the result of multiplying the weights), matching the logic in
+					// `recalculate_valid_point_count`.
 					total_weight += (*max_bucket as u64) * (*max_bucket as u64)
 						* (min_liquidity_offset_history_buckets[0] as u64) * (min_liquidity_offset_history_buckets[0] as u64);
 				}
@@ -2015,16 +2022,20 @@ mod bucketed_history {
 				let min_bucket_start_pos = BUCKET_START_POS[min_idx];
 				for (max_idx, max_bucket) in max_liquidity_offset_history_buckets.iter().enumerate().take(32 - min_idx) {
 					let max_bucket_end_pos = BUCKET_START_POS[32 - max_idx] - 1;
-					let mut bucket_weight = (*min_bucket as u64) * (*max_bucket as u64);
-					bucket_weight *= bucket_weight;
-					debug_assert!(bucket_weight as f64 <= total_valid_points_tracked);
-
 					if payment_pos >= max_bucket_end_pos {
 						// Success probability 0, the payment amount may be above the max liquidity
 						break;
 					}
 
+					// In testing, raising the weights of buckets to a high power led to better
+					// scoring results. Thus, we raise the bucket weights to the 4th power here (by
+					// squaring the result of multiplying the weights), matching the logic in
+					// `recalculate_valid_point_count`.
+					let mut bucket_weight = (*min_bucket as u64) * (*max_bucket as u64);
+					bucket_weight *= bucket_weight;
+					debug_assert!(bucket_weight as f64 <= total_valid_points_tracked);
 					let bucket_prob = bucket_weight as f64 / total_valid_points_tracked;
+
 					if payment_pos < min_bucket_start_pos {
 						cumulative_success_prob += bucket_prob;
 					} else {