diff --git a/examples/benchmarks/lib/benchmarks/knights.ak b/examples/benchmarks/lib/benchmarks/knights.ak
index d99b2ec8..f6d01146 100644
--- a/examples/benchmarks/lib/benchmarks/knights.ak
+++ b/examples/benchmarks/lib/benchmarks/knights.ak
@@ -7,11 +7,11 @@ use benchmarks/queue.{
 }
 
 test run_knights0() {
-  run_knights(0, 0) == []
+  run_knights(100, 0) == []
 }
 
 test run_knights1() {
-  run_knights(2, 2) == []
+  run_knights(100, 2) == []
 }
 
 fn run_knights(depth: Int, board_size: Int) -> Solution {
diff --git a/examples/benchmarks/lib/benchmarks/knights/chess_set.ak b/examples/benchmarks/lib/benchmarks/knights/chess_set.ak
index 465758e7..8d9454b1 100644
--- a/examples/benchmarks/lib/benchmarks/knights/chess_set.ak
+++ b/examples/benchmarks/lib/benchmarks/knights/chess_set.ak
@@ -25,6 +25,18 @@ pub fn first_piece(board: ChessSet) -> Tile {
   tile
 }
 
+// {-# INLINABLE lastPiece #-}
+// lastPiece :: ChessSet -> Tile
+// lastPiece (Board _ _ _ (t:_)) = t
+// lastPiece _                   = Tx.error ()
+
+pub fn last_piece(board: ChessSet) -> Tile {
+  when board.visited is {
+    [] -> fail
+    [x, ..] -> x
+  }
+}
+
 pub fn delete_first(board: ChessSet) -> ChessSet {
   let ChessSet { move_number, visited, .. } = board
 
@@ -64,71 +76,10 @@ pub fn is_square_free(board: ChessSet, tile: Tile) -> Bool {
 pub fn not_in(tiles: List<a>, tile: a) -> Bool {
   !list.has(tiles, tile)
 }
-// {-# INLINABLE createBoard #-}
-// createBoard :: Integer -> Tile -> ChessSet
-// createBoard x t = Board x 1 (Just t) [t]
-
-// {-# INLINABLE sizeBoard #-}
-// sizeBoard :: ChessSet -> Integer
-// sizeBoard (Board s _ _ _) = s
-
-// {-# INLINABLE noPieces #-}
-// noPieces :: ChessSet -> Integer
-// noPieces (Board _ n _ _) = n
-
-// {-# INLINABLE addPiece #-}
-// addPiece :: Tile -> ChessSet -> ChessSet
-// addPiece t (Board s n f ts) = Board s (n+1) f (t:ts)
-
-// -- % Remove the last element from a list
-// {-# INLINABLE init #-}
-// init :: [a] -> [a]
-// init l = case reverse l of
-//            _:as -> reverse as
-//            []   -> Tx.error ()
-
-// {-# INLINABLE secondLast #-}
-// secondLast :: [a] -> Maybe a
-// secondLast l =
-//     case reverse l of
-//       []    -> Tx.error ()
-//       [_]   -> Nothing
-//       _:a:_ -> Just a
-
-// {-%  Note [deleteFirst].
-//     deleteFirst removes the first position from the tour.
-//     Since the sequence of positions (ts) is stored in reverse this involves
-//     deleting the last element of ts and also storing the second-last element of
-//     ts as the new starting position.  In the strict world this will *fail* if the
-//     length of ts is 1.  The lazy version got away with this because the starting
-//     position is never examined in that case (possibly just through luck: with
-//     enough backtracking that might still happen).  To solve this we have to store
-//     the starting position as a Maybe value, deferring any error until we actually
-//     look at it.
-// %-}
-
-// {-# INLINABLE deleteFirst #-}
-// deleteFirst :: ChessSet -> ChessSet
-// deleteFirst (Board s n _ ts) =
-//     Board s (n-1) f' ts'
-//         where ts' = init ts
-//               f' = secondLast ts
-
 // {-# INLINABLE positionPiece #-}
 // positionPiece :: Integer -> ChessSet -> Tile
 // positionPiece x (Board _ n _ ts) = ts Tx.!! (n - x)
 
-// {-# INLINABLE lastPiece #-}
-// lastPiece :: ChessSet -> Tile
-// lastPiece (Board _ _ _ (t:_)) = t
-// lastPiece _                   = Tx.error ()
-
-// {-# INLINABLE firstPiece #-}
-// firstPiece :: ChessSet -> Tile
-// firstPiece (Board _ _ f _) =
-//     case f of Just tile -> tile
-//               Nothing   -> Tx.error ()
-
 // {-# INLINABLE pieceAtTile #-}
 // pieceAtTile :: Tile -> ChessSet -> Integer
 // pieceAtTile x0 (Board _ _ _ ts)
@@ -139,15 +90,6 @@ pub fn not_in(tiles: List<a>, tile: a) -> Bool {
 //            | x == y    = 1 + Tx.length xs
 //            | otherwise = findPiece x xs
 
-// {-# INLINABLE notIn #-}
-// notIn :: Eq a => a  -> [a] -> Bool
-// notIn _ []     = True
-// notIn x (a:as) = (x /= a) && (notIn x as)
-
-// {-# INLINABLE isSquareFree #-}
-// isSquareFree :: Tile -> ChessSet -> Bool
-// isSquareFree x (Board _ _ _ ts) = notIn x ts
-
 // -- % Everything below here is only needed for printing boards.
 // -- % This is useful for debugging.
 
diff --git a/examples/benchmarks/lib/benchmarks/knights/heuristic.ak b/examples/benchmarks/lib/benchmarks/knights/heuristic.ak
index 37d27f22..9099b24a 100644
--- a/examples/benchmarks/lib/benchmarks/knights/heuristic.ak
+++ b/examples/benchmarks/lib/benchmarks/knights/heuristic.ak
@@ -1,7 +1,7 @@
 use aiken/builtin
 use aiken/list
 use benchmarks/knights/chess_set.{
-  add_piece, create_board, delete_first, first_piece, is_square_free,
+  add_piece, create_board, delete_first, first_piece, is_square_free, last_piece,
 }
 use benchmarks/knights/sort.{quick_sort}
 use benchmarks/knights/types.{ChessSet, Tile}
@@ -17,6 +17,10 @@ type Direction {
   RD
 }
 
+fn direction_list() {
+  [UL, UR, DL, DR, LU, LD, RU, RD]
+}
+
 fn move(direction: Direction, tile: Tile) -> Tile {
   let (x, y) = tile
 
@@ -111,6 +115,10 @@ pub fn can_move_to(board: ChessSet, tile: Tile) -> Bool {
   }
 }
 
+fn can_move(board: ChessSet, direction: Direction) -> Bool {
+  board |> can_move_to(move(direction, last_piece(board)))
+}
+
 pub fn all_descend(board: ChessSet) -> List<ChessSet> {
   board
     |> possible_moves
@@ -118,94 +126,9 @@ pub fn all_descend(board: ChessSet) -> List<ChessSet> {
 }
 
 fn move_knight(board: ChessSet, direction: Direction) -> ChessSet {
-  todo
+  add_piece(board, move(direction, last_piece(board)))
 }
 
 fn possible_moves(board: ChessSet) -> List<Direction> {
-  todo
+  direction_list() |> list.filter(fn(direction) { can_move(board, direction) })
 }
-// data Direction = UL | UR | DL |DR | LU | LD | RU | RD
-
-// {-# INLINABLE move #-}
-// move :: Direction -> Tile -> Tile
-// move UL (x,y) = (x-1,y-2)
-// move UR (x,y) = (x+1,y-2)
-// move DL (x,y) = (x-1,y+2)
-// move DR (x,y) = (x+1,y+2)
-// move LU (x,y) = (x-2,y-1)
-// move LD (x,y) = (x-2,y+1)
-// move RU (x,y) = (x+2,y-1)
-// move RD (x,y) = (x+2,y+1)
-
-// {-# INLINABLE startTour #-}
-// startTour :: Tile -> Integer -> ChessSet
-// startTour st size
-//    | (size `Tx.remainder` 2) == 0 = createBoard size st
-//    | otherwise           = {-Tx.trace "startTour" $ -} Tx.error ()
-
-// {-# INLINABLE moveKnight #-}
-// moveKnight :: ChessSet -> Direction -> ChessSet
-// moveKnight board dir
-//    = addPiece (move dir (lastPiece board)) board
-
-// {-# INLINABLE canMove #-}
-// canMove :: ChessSet -> Direction -> Bool
-// canMove board dir
-//    = canMoveTo (move dir (lastPiece board)) board
-
-// {-# INLINABLE canMoveTo #-}
-// canMoveTo :: Tile -> ChessSet -> Bool
-// canMoveTo t@(x,y) board
-//    = (x Tx.>= 1) && (x Tx.<= sze) &&
-//      (y Tx.>= 1) && (y Tx.<= sze) &&
-//      isSquareFree t board
-//      where
-//         sze = sizeBoard board
-
-// {-# INLINABLE descendents #-}
-// descendents :: ChessSet -> [ChessSet]
-// descendents board =
-//   if (canJumpFirst board) && (deadEnd (addPiece (firstPiece board) board))
-//   then []
-//   else
-//       let l = Tx.length singles in
-//       if l == 0 then map snd (quickSort (descAndNo board))
-//       else if l == 1 then singles
-//            else []           -- Going to be dead end
-//                where
-//                  singles = singleDescend board
-
-// {-# INLINABLE singleDescend #-}
-// singleDescend :: ChessSet -> [ChessSet]
-// singleDescend board =[x | (y,x) <- descAndNo board, y==1]
-
-// {-# INLINABLE descAndNo #-}
-// descAndNo :: ChessSet -> [(Integer,ChessSet)]
-// descAndNo board
-//    = [(Tx.length (possibleMoves (deleteFirst x)),x) | x <- allDescend board]
-
-// {-# INLINABLE allDescend #-}
-// allDescend :: ChessSet -> [ChessSet]
-// allDescend board
-//    =  map (moveKnight board) (possibleMoves board)
-
-// {-# INLINABLE possibleMoves #-}
-// possibleMoves :: ChessSet -> [Direction]
-// possibleMoves board
-//    =[x | x <- [UL,UR,DL,DR,LU,LD,RU,RD], (canMove board x)]
-
-// {-# INLINABLE deadEnd #-}
-// deadEnd :: ChessSet -> Bool
-// deadEnd board = (Tx.length (possibleMoves board)) == 0
-
-// {-# INLINABLE canJumpFirst #-}
-// canJumpFirst :: ChessSet -> Bool
-// canJumpFirst board
-//   = canMoveTo (firstPiece board) (deleteFirst board)
-
-// {-# INLINABLE tourFinished #-}
-// tourFinished :: ChessSet -> Bool
-// tourFinished board
-//    = (noPieces board == (sze*sze)) && (canJumpFirst board)
-//      where
-//         sze = sizeBoard board