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Merge pull request #51 from ethereum/JustinDrake-patch-4 

Cleanups in "State recalculations"
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Danny Ryan 2018-10-08 21:42:49 -04:00 committed by GitHub
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@ -521,45 +521,52 @@ Repeat while `slot - last_state_recalculation_slot >= CYCLE_LENGTH`:
#### Adjust justified slots and crosslink status #### Adjust justified slots and crosslink status
For all slots `s` in `last_state_recalculation_slot - CYCLE_LENGTH ... last_state_recalculation_slot - 1`: For every slot `s` in the range `last_state_recalculation_slot - CYCLE_LENGTH ... last_state_recalculation_slot - 1`:
* Determine the total set of validators that attested to that block at least once * Let `total_balance` be the total balance of active validators.
* Determine the total balance of these validators. If this value times three equals or exceeds the total balance of all active validators times two, set `last_justified_slot = max(last_justified_slot, s)` and `justified_streak += 1`. Otherwise, set `justified_streak = 0` * Let `total_balance_attesting_at_s` be the total balance of validators that attested to the beacon chain block at slot `s`.
* If `justified_streak >= CYCLE_LENGTH + 1`, set `last_finalized_slot = max(last_finalized_slot, s - CYCLE_LENGTH - 1)` * If `3 * total_balance_attesting_at_s >= 2 * total_balance` set `last_justified_slot = max(last_justified_slot, s)` and `justified_streak += 1`. Otherwise set `justified_streak = 0`.
* If `justified_streak >= CYCLE_LENGTH + 1` set `last_finalized_slot = max(last_finalized_slot, s - CYCLE_LENGTH - 1)`.
For all (`shard`, `shard_block_hash`) tuples, compute the total deposit size of validators that attested to that block hash for that shard. If this value times three equals or exceeds the total balance of all validators in the committee times two, and the current dynasty exceeds `crosslinks[shard].dynasty`, set `crosslinks[shard] = CrosslinkRecord(dynasty=dynasty, slot=block.last_state_recalculation_slot + CYCLE_LENGTH, hash=shard_block_hash)`. For every `(shard, shard_block_hash)` tuple:
* Let `total_balance_attesting_to_h` be the total balance of validators that attested to the shard block with hash `shard_block_hash`.
* Let `total_committee_balance` be the total balance in the committee of validators that could have attested to the shard block with hash `shard_block_hash`.
* If `3 * total_balance_attesting_to_h >= 2 * total_committee_balance` and `dynasty > crosslinks[shard].dynasty`, set `crosslinks[shard] = CrosslinkRecord(dynasty=dynasty, slot=block.last_state_recalculation_slot + CYCLE_LENGTH, hash=shard_block_hash)`.
#### Balance recalculations related to FFG rewards #### Balance recalculations related to FFG rewards
Let `time_since_finality = block.slot - last_finalized_slot`, and let `B` be the balance of any given validator whose balance we are adjusting, not including any balance changes from this round of state recalculation. Let: * Let `total_balance` be the total balance of active validators.
* Let `total_balance_in_eth = total_balance // GWEI_PER_ETH.
* Let `reward_quotient = BASE_REWARD_QUOTIENT * int_sqrt(total_balance_in_eth)`. (The per-slot maximum interest rate is `1/reward_quotient`.)
* Let `quadratic_penalty_quotient = SQRT_E_DROP_TIME**2`. (The portion lost by offline validators after `D` slots is about `D*D/2/quadratic_penalty_quotient`.)
* Let `time_since_finality = block.slot - last_finalized_slot`.
* `total_deposits = sum([v.balance for i, v in enumerate(validators) if i in get_active_validator_indices(validators, dynasty)])` and `total_deposits_in_ETH = total_deposits // GWEI_PER_ETH` For every slot `s` in the range `last_state_recalculation_slot - CYCLE_LENGTH ... last_state_recalculation_slot - 1`:
* `reward_quotient = BASE_REWARD_QUOTIENT * int_sqrt(total_deposits_in_ETH)` (`1/reward_quotient` is the per-slot max interest rate)
* `quadratic_penalty_quotient = SQRT_E_DROP_TIME**2` (after `D` slots about `D*D/2/quadratic_penalty_quotient` is the portion lost by offline validators)
For each slot `S` in the range `last_state_recalculation_slot - CYCLE_LENGTH ... last_state_recalculation_slot - 1`: * Let `total_balance_participating` be the total balance of validators that voted for the canonical beacon chain block at slot `s`. In the normal case every validator will be in one of the `CYCLE_LENGTH` slots following slot `s` and so can vote for a block at slot `s`.
* Let `B` be the balance of any given validator whose balance we are adjusting, not including any balance changes from this round of state recalculation.
* If `time_since_finality <= 3 * CYCLE_LENGTH` adjust the balance of participating and non-participating validators as follows:
* Participating validators gain `B // reward_quotient * (2 * total_balance_participating - total_balance) // total_balance`. (Note that this value may be negative.)
* Non-participating validators lose `B // reward_quotient`.
* Otherwise:
* Participating validators gain nothing.
* Non-participating validators lose `B // reward_quotient + B * time_since_finality // quadratic_penalty_quotient`.
* Let `total_participated_deposits` be the total balance of validators that voted for the correct hash in slot `S` (ie. the hash that actually is the hash of the block at that slot in the current chain); note that in the normal case, every validator will be in one of the `CYCLE_LENGTH` slots following the slot and so can vote for a hash in slot `S`. If `time_since_finality <= 3 * CYCLE_LENGTH`, then adjust participating and non-participating validators' balances as follows: In addition, validators with `status == PENALIZED` lose `B // reward_quotient + B * time_since_finality // quadratic_penalty_quotient`.
* Participating validators gain `B // reward_quotient * (2 * total_participated_deposits - total_deposits) // total_deposits` (note: this may be negative)
* Nonparticipating validators lose `B // reward_quotient`
* Otherwise, adjust as follows:
* Participating validators' balances are unchanged
* Nonparticipating validators lose `B // reward_quotient + B * time_since_finality // quadratic_penalty_quotient`
Validators with `status == PENALIZED` also lose `B // reward_quotient + B * time_since_finality // quadratic_penalty_quotient`.
#### Balance recalculations related to crosslink rewards #### Balance recalculations related to crosslink rewards
For each shard `S` for which a crosslink committee exists in the cycle prior to the most recent cycle (`last_state_recalculation_slot - CYCLE_LENGTH ... last_state_recalculation_slot - 1`), let `V` be the corresponding validator set. Let `B` be the balance of any given validator whose balance we are adjusting, not including any balance changes from this round of state recalculation. For each `S`, `V`: For every shard number `shard` for which a crosslink committee exists in the cycle prior to the most recent cycle (`last_state_recalculation_slot - CYCLE_LENGTH ... last_state_recalculation_slot - 1`), let `V` be the corresponding validator set. Let `B` be the balance of any given validator whose balance we are adjusting, not including any balance changes from this round of state recalculation. For each `shard`, `V`:
* Let `total_v_deposits` be the total balance of `V` * Let `total_balance_of_v` be the total balance of `V`.
* Let `total_participated_v_deposits` be the total balance of the subset of `V` that participated (note that `total_participated_v_deposits <= total_v_deposits`) * Let `total_balance_of_v_participating` be the total balance of the subset of `V` that participated.
* Let `time_since_last_confirmation` be `block.slot - crosslinks[S].slot` * Let `time_since_last_confirmation = block.slot - crosslinks[shard].slot`.
* Adjust balances as follows: * If `dynasty > crosslinks[shard].dynasty` adjust balances as follows:
* If `crosslinks[S].dynasty == dynasty`, no reward adjustments * Participating validators gain `B // reward_quotient * (2 * total_balance_of_v_participating - total_balance_of_v) // total_balance_of_v`.
* Otherwise, participating validators' balances are increased by `B // reward_quotient * (2 * total_participated_v_deposits - total_v_deposits) // total_v_deposits`, and the balances of non-participating validators are decreased by `B // reward_quotient + B * time_since_last_confirmation // quadratic_penalty_quotient` * Non-participating validators lose `B // reward_quotient + B * time_since_last_confirmation // quadratic_penalty_quotient`.
Let `committees` be the set of committees processed and `time_since_last_confirmation(c)` be the value of `time_since_last_confirmation` in that committee. Validators with `status == PENALIZED` lose `B // reward_quotient + B * sum([time_since_last_confirmation(c) for c in committees]) // len(committees) // quadratic_penalty_quotient`. In addition, validators with `status == PENALIZED` lose `B // reward_quotient + B * sum([time_since_last_confirmation(c) for c in committees]) // len(committees) // quadratic_penalty_quotient`, where `committees` is the set of committees processed and `time_since_last_confirmation(c)` is the value of `time_since_last_confirmation` in committee `c`.
#### Process penalties, logouts and other special objects #### Process penalties, logouts and other special objects
@ -586,7 +593,7 @@ A dynasty transition can happen after a state recalculation if all of the follow
* `block.slot - crystallized_state.dynasty_start_slot >= MIN_DYNASTY_LENGTH` * `block.slot - crystallized_state.dynasty_start_slot >= MIN_DYNASTY_LENGTH`
* `last_finalized_slot > dynasty_start_slot` * `last_finalized_slot > dynasty_start_slot`
* For every shard `S` in `shard_and_committee_for_slots`, `crosslinks[S].slot > dynasty_start_slot` * For every shard number `shard` in `shard_and_committee_for_slots`, `crosslinks[shard].slot > dynasty_start_slot`
Then, run the following algorithm to update the validator set: Then, run the following algorithm to update the validator set:
@ -594,12 +601,12 @@ Then, run the following algorithm to update the validator set:
def change_validators(validators): def change_validators(validators):
# The active validator set # The active validator set
active_validators = get_active_validator_indices(validators, dynasty) active_validators = get_active_validator_indices(validators, dynasty)
# The total size of active deposits # The total balance of active validators
total_deposits = sum([v.balance for i, v in enumerate(validators) if i in active_validators]) total_balance = sum([v.balance for i, v in enumerate(validators) if i in active_validators])
# The maximum total Gwei that can be deposited and withdrawn # The maximum total wei that can deposit+withdraw
max_allowable_change = max( max_allowable_change = max(
2 * DEPOSIT_SIZE * GWEI_PER_ETH, 2 * DEPOSIT_SIZE GWEI_PER_ETH,
total_deposits // MAX_VALIDATOR_CHURN_QUOTIENT total_balance // MAX_VALIDATOR_CHURN_QUOTIENT
) )
# Go through the list start to end depositing+withdrawing as many as possible # Go through the list start to end depositing+withdrawing as many as possible
total_changed = 0 total_changed = 0
@ -628,7 +635,7 @@ def change_validators(validators):
for i in range(len(validators)): for i in range(len(validators)):
if validators[i].status in (PENDING_WITHDRAW, PENALIZED) and current_slot >= validators[i].exit_slot + WITHDRAWAL_PERIOD: if validators[i].status in (PENDING_WITHDRAW, PENALIZED) and current_slot >= validators[i].exit_slot + WITHDRAWAL_PERIOD:
if validators[i].status == PENALIZED: if validators[i].status == PENALIZED:
validators[i].balance -= validators[i].balance * min(total_penalties * 3, total_deposits) // total_deposits validators[i].balance -= validators[i].balance * min(total_penalties * 3, total_balance) // total_balance
validators[i].status = WITHDRAWN validators[i].status = WITHDRAWN
withdraw_amount = validators[i].balance withdraw_amount = validators[i].balance