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Co-authored-by: Danny Ryan <dannyjryan@gmail.com>
This commit is contained in:
Aditya Asgaonkar
2023-03-14 13:54:57 -07:00
committed by GitHub
parent 23c5b7c66e
commit 3de96f7a19
1 changed files with 18 additions and 28 deletions
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specs/phase0/fork-choice.md
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@@ -107,9 +107,9 @@ def is_previous_epoch_justified(store: Store) -> bool:
The `Store` is responsible for tracking information required for the fork choice algorithm. The important fields being tracked are described below:
- `justified_checkpoint`: the justified checkpoint being used as the starting point for the LMD GHOST fork choice algorithm.
- `finalized_checkpoint`: the highest finalized checkpoint that was seen. In general, the fork choice will consider only those blocks that are not conflicting with this checkpoint.
- `unrealized_justified_checkpoint` & `unrealized_finalized_checkpoint`: these track the highest justified & finalized checkpoints resp., without regard to whether on-chain ***realization***, i.e., FFG processing of new attestations, has occurred. This is an important distinction from `justified_checkpoint` & `finalized_checkpoint`, because they will only track the checkpoints that are realized on-chain. Note that on-chain processing of FFG information only happens at epoch boundaries.
- `justified_checkpoint`: the justified checkpoint used as the starting point for the LMD GHOST fork choice algorithm.
- `finalized_checkpoint`: the highest known finalized checkpoint. The fork choice only considers blocks that are not conflicting with this checkpoint.
- `unrealized_justified_checkpoint` & `unrealized_finalized_checkpoint`: these track the highest justified & finalized checkpoints resp., without regard to whether on-chain ***realization*** has occurred, i.e. FFG processing of new attestations within the state transition function. This is an important distinction from `justified_checkpoint` & `finalized_checkpoint`, because they will only track the checkpoints that are realized on-chain. Note that on-chain processing of FFG information only happens at epoch boundaries.
- `unrealized_justifications`: stores a map of block root to the unrealized justified checkpoint observed in that block.
```python
@@ -229,18 +229,16 @@ def get_weight(store: Store, root: Root) -> Gwei:
```python
def get_voting_source(store: Store, block_root: Root) -> Checkpoint:
"""
Compute the voting source checkpoint in the case that block with root ``block_root``
is chosen as the head block
Compute the voting source checkpoint in event that block with root ``block_root`` is the head block
"""
block = store.blocks[block_root]
current_epoch = compute_epoch_at_slot(get_current_slot(store))
block_epoch = compute_epoch_at_slot(block.slot)
if current_epoch > block_epoch:
# The block is from a prior epoch, the voting source will be pulled-up.
# The block is from a prior epoch, the voting source will be pulled-up
return store.unrealized_justifications[block_root]
else:
# The block is not from a prior epoch, therefore the voting source is
# not pulled up.
# The block is not from a prior epoch, therefore the voting source is not pulled up
head_state = store.block_states[block_root]
return head_state.current_justified_checkpoint
@@ -248,7 +246,7 @@ def get_voting_source(store: Store, block_root: Root) -> Checkpoint:
#### `filter_block_tree`
*Note*: External calls to `filter_block_tree` (i.e., any calls that are not made by the recursive logic in this function) MUST have `block_root` as `store.justified_checkpoint`.
*Note*: External calls to `filter_block_tree` (i.e., any calls that are not made by the recursive logic in this function) MUST set `block_root` to `store.justified_checkpoint`.
```python
def filter_block_tree(store: Store, block_root: Root, blocks: Dict[Root, BeaconBlock]) -> bool:
@@ -270,7 +268,7 @@ def filter_block_tree(store: Store, block_root: Root, blocks: Dict[Root, BeaconB
current_epoch = compute_epoch_at_slot(get_current_slot(store))
voting_source = get_voting_source(store, block_root)
# The voting source should be at the same height as the store's justified checkpoint.
# The voting source should be at the same height as the store's justified checkpoint
correct_justified = (
store.justified_checkpoint.epoch == GENESIS_EPOCH
or voting_source.epoch == store.justified_checkpoint.epoch
@@ -378,20 +376,16 @@ def compute_pulled_up_tip(store: Store, block_root: Root) -> None:
# Pull up the post-state of the block to the next epoch boundary
process_justification_and_finalization(state)
# Store the unrealized justification.
store.unrealized_justifications[block_root] = state.current_justified_checkpoint
# Update unrealized checkpoints in store if necessary
update_unrealized_checkpoints(store, state.current_justified_checkpoint, state.finalized_checkpoint)
# If the block is from a prior epoch, apply the realized values.
# If the block is from a prior epoch, apply the realized values
block_epoch = compute_epoch_at_slot(store.blocks[block_root].slot)
current_epoch = compute_epoch_at_slot(get_current_slot(store))
if block_epoch < current_epoch:
update_checkpoints(store, state.current_justified_checkpoint, state.finalized_checkpoint)
```
#### `on_tick` helpers
##### `on_tick_per_slot`
@@ -400,21 +394,18 @@ def compute_pulled_up_tip(store: Store, block_root: Root) -> None:
def on_tick_per_slot(store: Store, time: uint64) -> None:
previous_slot = get_current_slot(store)
# update store time
# Update store time
store.time = time
current_slot = get_current_slot(store)
# Reset store.proposer_boost_root if this is a new slot
# If this is a new slot, reset store.proposer_boost_root
if current_slot > previous_slot:
store.proposer_boost_root = Root()
# Not a new epoch, return
if not (current_slot > previous_slot and compute_slots_since_epoch_start(current_slot) == 0):
return
# Pull-up justification and finalization from previous epoch
update_checkpoints(store, store.unrealized_justified_checkpoint, store.unrealized_finalized_checkpoint)
# If a new epoch, pull-up justification and finalization from previous epoch
if current_slot > previous_slot and compute_slots_since_epoch_start(current_slot) == 0:
update_checkpoints(store, store.unrealized_justified_checkpoint, store.unrealized_finalized_checkpoint)
```
#### `on_attestation` helpers
@@ -447,8 +438,7 @@ def validate_on_attestation(store: Store, attestation: Attestation, is_from_bloc
# Check that the epoch number and slot number are matching
assert target.epoch == compute_epoch_at_slot(attestation.data.slot)
# Attestations target be for a known block.
# If target block is unknown, delay consideration until the block is found.
# Attestation target must be for a known block. If target block is unknown, delay consideration until block is found
assert target.root in store.blocks
# Attestations must be for a known block. If block is unknown, delay consideration until the block is found
@@ -498,8 +488,8 @@ def update_latest_messages(store: Store,
```python
def on_tick(store: Store, time: uint64) -> None:
# If the ``store.time`` falls behind, catch up slot by slot to
# ensure that every previous slot will be processed with ``on_tick_per_slot``.
# If the ``store.time`` falls behind, while loop catches up slot by slot
# to ensure that every previous slot is processed with ``on_tick_per_slot``
tick_slot = (time - store.genesis_time) // SECONDS_PER_SLOT
while get_current_slot(store) < tick_slot:
previous_time = store.genesis_time + (get_current_slot(store) + 1) * SECONDS_PER_SLOT
@@ -543,7 +533,7 @@ def on_block(store: Store, signed_block: SignedBeaconBlock) -> None:
# Update checkpoints in store if necessary
update_checkpoints(store, state.current_justified_checkpoint, state.finalized_checkpoint)
# Eagerly compute unrealized justification and finality.
# Eagerly compute unrealized justification and finality
compute_pulled_up_tip(store, block_root)
```