tracing chain quality about cardano-node HOT 4 CLOSED

import Ouroboros.Network.Point (fromWithOrigin)

chainDensity :: HasHeader blk
             => AnchoredFragment (Header blk) -> Maybe Rational
chainDensity frag
    | slots == 0
    = Nothing
    | otherwise
    = Just $ toRational blocks / toRational slots
  where
    -- Slot of the tip - slot @k@ blocks back. Use 0 as the slot for genesis
    slots  = unSlotNo (fromWithOrigin 0 (AF.headSlot frag))
           - unSlotNo (fromWithOrigin 0 (pointSlot (AF.anchorPoint frag)))
    -- Includes EBBs
    blocks = AF.length frag

import Ouroboros.Network.Point (fromWithOrigin)

chainDensity :: HasHeader blk
             => AnchoredFragment (Header blk) -> Maybe Rational
chainDensity frag
    | slots == 0
    = Nothing
    | otherwise
    = Just $ toRational blocks / toRational slots
  where
    -- Slot of the tip - slot @k@ blocks back. Use 0 as the slot for genesis
    slots  = unSlotNo (fromWithOrigin 0 (AF.headSlot frag))
           - unSlotNo (fromWithOrigin 0 (AF.lastSlot frag))
    blocks = unBlockNo (fromMaybe 0 (AF.headBlockNo frag))
           - unBlockNo (either (const 0) blockNo (AF.last frag))

    ... -- unchanged
    -- Block numbers start at 1. We ignore the genesis EBB, which has block number 0.
    blocks = unBlockNo (fromMaybe 1 (AF.headBlockNo frag))
           - case unBlockNo . blockNo <$> AF.last frag of
               -- Empty fragment, no blocks. We have that @blocks = 1 - 1 = 0@
               Left _ -> 1
               -- The oldest block is the genesis EBB with block number 0,
               -- don't let it contribute to the number of blocks
               Right 0 -> 1
               Right b -> b