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Justification bitvector length to constant

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Dankrad Feist 2019-06-27 13:09:48 +01:00
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1 changed files with 5 additions and 4 deletions
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9
specs/core/0_beacon-chain.md
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@ -189,6 +189,7 @@ The following values are (non-configurable) constants used throughout the specif
| `MIN_PER_EPOCH_CHURN_LIMIT` | `2**2` (= 4) | | `MIN_PER_EPOCH_CHURN_LIMIT` | `2**2` (= 4) |
| `CHURN_LIMIT_QUOTIENT` | `2**16` (= 65,536) | | `CHURN_LIMIT_QUOTIENT` | `2**16` (= 65,536) |
| `SHUFFLE_ROUND_COUNT` | `90` | | `SHUFFLE_ROUND_COUNT` | `90` |
| `JUSTIFICATION_BITVECTOR_LENGTH` | `4` |
* For the safety of crosslinks, `TARGET_COMMITTEE_SIZE` exceeds [the recommended minimum committee size of 111](https://vitalik.ca/files/Ithaca201807_Sharding.pdf); with sufficient active validators (at least `SLOTS_PER_EPOCH * TARGET_COMMITTEE_SIZE`), the shuffling algorithm ensures committee sizes of at least `TARGET_COMMITTEE_SIZE`. (Unbiasable randomness with a Verifiable Delay Function (VDF) will improve committee robustness and lower the safe minimum committee size.) * For the safety of crosslinks, `TARGET_COMMITTEE_SIZE` exceeds [the recommended minimum committee size of 111](https://vitalik.ca/files/Ithaca201807_Sharding.pdf); with sufficient active validators (at least `SLOTS_PER_EPOCH * TARGET_COMMITTEE_SIZE`), the shuffling algorithm ensures committee sizes of at least `TARGET_COMMITTEE_SIZE`. (Unbiasable randomness with a Verifiable Delay Function (VDF) will improve committee robustness and lower the safe minimum committee size.)
@ -523,7 +524,7 @@ class BeaconState(Container):
previous_justified_root: Hash # Previous epoch snapshot previous_justified_root: Hash # Previous epoch snapshot
current_justified_epoch: Epoch current_justified_epoch: Epoch
current_justified_root: Hash current_justified_root: Hash
justification_bitfield: Bitvector[4] # Bit set for every recent justified epoch justification_bitfield: Bitvector[JUSTIFICATION_BITVECTOR_LENGTH] # Bit set for every recent justified epoch
# Finality # Finality
finalized_epoch: Epoch finalized_epoch: Epoch
finalized_root: Hash finalized_root: Hash
@ -1291,21 +1292,21 @@ def process_justification_and_finalization(state: BeaconState) -> None:
# Process justifications # Process justifications
state.previous_justified_epoch = state.current_justified_epoch state.previous_justified_epoch = state.current_justified_epoch
state.previous_justified_root = state.current_justified_root state.previous_justified_root = state.current_justified_root
state.justification_bitfield = Bitvector[4](*([0] + state.justification_bitfield[0:3])) state.justification_bitfield = Bitvector[4](*([0b0] + state.justification_bitfield[0:JUSTIFICATION_BITVECTOR_LENGTH - 1]))
previous_epoch_matching_target_balance = get_attesting_balance( previous_epoch_matching_target_balance = get_attesting_balance(
state, get_matching_target_attestations(state, previous_epoch) state, get_matching_target_attestations(state, previous_epoch)
) )
if previous_epoch_matching_target_balance * 3 >= get_total_active_balance(state) * 2: if previous_epoch_matching_target_balance * 3 >= get_total_active_balance(state) * 2:
state.current_justified_epoch = previous_epoch state.current_justified_epoch = previous_epoch
state.current_justified_root = get_block_root(state, state.current_justified_epoch) state.current_justified_root = get_block_root(state, state.current_justified_epoch)
state.justification_bitfield[1] = True state.justification_bitfield[1] = 0b1
current_epoch_matching_target_balance = get_attesting_balance( current_epoch_matching_target_balance = get_attesting_balance(
state, get_matching_target_attestations(state, current_epoch) state, get_matching_target_attestations(state, current_epoch)
) )
if current_epoch_matching_target_balance * 3 >= get_total_active_balance(state) * 2: if current_epoch_matching_target_balance * 3 >= get_total_active_balance(state) * 2:
state.current_justified_epoch = current_epoch state.current_justified_epoch = current_epoch
state.current_justified_root = get_block_root(state, state.current_justified_epoch) state.current_justified_root = get_block_root(state, state.current_justified_epoch)
state.justification_bitfield[0] = True state.justification_bitfield[0] = 0b1
# Process finalizations # Process finalizations
bitfield = state.justification_bitfield bitfield = state.justification_bitfield