Do not recompute intersections on good jumps

IntersectMBO · Apr 25, 2024 · ac4105e · ac4105e
1 parent af0cf93
commit ac4105e
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Showing 2 changed files with 19 additions and 7 deletions.
diff --git a/...os-consensus/src/ouroboros-consensus/Ouroboros/Consensus/MiniProtocol/ChainSync/Client.hs b/...os-consensus/src/ouroboros-consensus/Ouroboros/Consensus/MiniProtocol/ChainSync/Client.hs
@@ -1235,15 +1235,25 @@ knownIntersectionStateTop cfgEnv dynEnv intEnv =
                   HeaderStateHistory.rewind
                     (AF.castPoint $ AF.headPoint $ jTheirFragment ji)
                     (jTheirHeaderStateHistory ji)
-                intersection = case AF.intersect (jOurFragment ji) (jTheirFragment ji) of
-                  Just (po, _, _, _) -> castPoint $ AF.headPoint po
-                  Nothing -> error "offerJump: the jumpInfo should have a valid intersection"
+                rewoundHistory =
+                  fromMaybe (error "offerJump: cannot rewind history") mRewoundHistory
+                historyNeedsRewinding =
+                     (/= AF.headPoint (jTheirFragment ji)) $
+                     castPoint $
+                     either headerStatePoint headerStatePoint $
+                     AF.head $
+                     HeaderStateHistory.unHeaderStateHistory $
+                     jTheirHeaderStateHistory ji
+                intersection
+                  | historyNeedsRewinding = case AF.intersect (jOurFragment ji) (jTheirFragment ji) of
+                      Just (po, _, _, _) -> castPoint $ AF.headPoint po
+                      Nothing -> error "offerJump: the jumpInfo should have a valid intersection"
+                  | otherwise = jMostRecentIntersection ji
              in KnownIntersectionState
                   { mostRecentIntersection = intersection
                   , ourFrag = jOurFragment ji
                   , theirFrag = jTheirFragment ji
-                  , theirHeaderStateHistory =
-                      fromMaybe (error "offerJump: cannot rewind history") mRewoundHistory
+                  , theirHeaderStateHistory = rewoundHistory
                   , kBestBlockNo = max (fromWithOrigin 0 $ AF.headBlockNo $ jTheirFragment ji) (kBestBlockNo kis)
                   }
 
@@ -1477,7 +1487,8 @@ updateJumpInfoSTM ::
   -> STM m ()
 updateJumpInfoSTM jumping kis@KnownIntersectionState{ourFrag} =
     Jumping.jgUpdateJumpInfo jumping JumpInfo
-      { jOurFragment = ourFrag
+      { jMostRecentIntersection = mostRecentIntersection kis
+      , jOurFragment = ourFrag
       , jTheirFragment = theirFrag kis
       , jTheirHeaderStateHistory = theirHeaderStateHistory kis
       }

diff --git a/...sensus/src/ouroboros-consensus/Ouroboros/Consensus/MiniProtocol/ChainSync/Client/State.hs b/...sensus/src/ouroboros-consensus/Ouroboros/Consensus/MiniProtocol/ChainSync/Client/State.hs
@@ -124,7 +124,8 @@ deriving anyclass instance
 
 -- | The ChainSync state required for jumps
 data JumpInfo blk = JumpInfo
-  { jOurFragment :: !(AnchoredFragment (Header blk))
+  { jMostRecentIntersection :: !(Point blk)
+  , jOurFragment :: !(AnchoredFragment (Header blk))
   , jTheirFragment :: !(AnchoredFragment (Header blk))
   , jTheirHeaderStateHistory :: !(HeaderStateHistory blk)
   }