add merge functions

Author: joostjager

lightning/src/routing/scoring.rs

@@ -1130,6 +1130,15 @@ impl ChannelLiquidity {
 		}
 	}
 
+	fn merge(&mut self, other: &Self) {
+		// Take average for min/max liquidity offsets.
+		self.min_liquidity_offset_msat = (self.min_liquidity_offset_msat + other.min_liquidity_offset_msat) / 2;
+		self.max_liquidity_offset_msat = (self.max_liquidity_offset_msat + other.max_liquidity_offset_msat) / 2;
+
+		// Merge historical liquidity data.
+		self.liquidity_history.merge(&other.liquidity_history);
+	}
+
 	/// Returns a view of the channel liquidity directed from `source` to `target` assuming
 	/// `capacity_msat`.
 	fn as_directed(
@@ -1672,13 +1681,11 @@ impl<G: Deref<Target = NetworkGraph<L>>, L: Deref> CombinedScorer<G, L> where L:
     pub fn merge(&mut self, external_scores: HashMap<u64, ChannelLiquidity>) {
         let local_scores = &self.local_only_scorer.channel_liquidities;
 
-		for (scid, liquidity) in external_scores {
+		for (scid, mut liquidity) in external_scores {
 			if let Some(local_liquidity) = local_scores.get(&scid) {
-				let merged_liquidity = liquidity.merge(local_liquidity);
-				self.scorer.channel_liquidities.insert(scid, merged_liquidity);
-			} else {
-				self.scorer.channel_liquidities.insert(scid, liquidity);
+				liquidity.merge(local_liquidity);
 			}
+			self.scorer.channel_liquidities.insert(scid, liquidity);
 		}
     }
 }
@@ -1905,6 +1912,13 @@ mod bucketed_history {
 				self.buckets[bucket] = self.buckets[bucket].saturating_add(BUCKET_FIXED_POINT_ONE);
 			}
 		}
+
+		/// Returns the average of the buckets between the two trackers.
+		pub(crate) fn merge(&mut self, other: &Self) -> () {
+			for (index, bucket) in self.buckets.iter_mut().enumerate() {
+				*bucket = (*bucket + other.buckets[index]) / 2;
+			}
+		}
 	}
 
 	impl_writeable_tlv_based!(HistoricalBucketRangeTracker, { (0, buckets, required) });
@@ -2001,6 +2015,12 @@ mod bucketed_history {
 		-> DirectedHistoricalLiquidityTracker<&'a mut HistoricalLiquidityTracker> {
 			DirectedHistoricalLiquidityTracker { source_less_than_target, tracker: self }
 		}
+
+		pub fn merge(&mut self, other: &Self) {
+			self.min_liquidity_offset_history.merge(&other.min_liquidity_offset_history);
+			self.max_liquidity_offset_history.merge(&other.max_liquidity_offset_history);
+			self.recalculate_valid_point_count();
+		}
 	}
 
 	/// A set of buckets representing the history of where we've seen the minimum- and maximum-