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Update beacon-chain.md

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vbuterin 2018-10-30 04:45:28 -04:00 committed by GitHub
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@ -207,8 +207,8 @@ The `CrystallizedState` has the following fields:
# Committee members and their assigned shard, per slot
'shard_and_committee_for_slots': [[ShardAndCommittee]],
# Persistent shard committees
'current_persistent_committees': [['uint24']],
'next_persistent_committees': [['uint24']],
'persistent_committees': [['uint24']],
'shard_reassignment_records': [ShardReassignmentRecord],
# Total deposits penalized in the given withdrawal period
'deposits_penalized_in_period': ['uint32'],
# Hash chain of validator set changes (for light clients to easily track deltas)
@ -268,6 +268,19 @@ A `ShardAndCommittee` object has the following fields:
}
```
A `ShardReassignmentRecord` object has the following fields:
```python
{
# Which validator to reassign
'validator_id': 'uint64',
# To which shard
'shard': 'uint16',
# When
'slot': 'uint64'
}
```
## Beacon chain processing
The beacon chain is the "main chain" of the PoS system. The beacon chain's main responsibilities are:
@ -446,15 +459,6 @@ Here's a diagram of what's going on:
![](http://vitalik.ca/files/ShuffleAndAssign.png?1)
We also make a function for generating persistent committees:
```python
def get_persistent_shuffling(validators: List[ValidatorRecord], seed: Hash32) -> List[List[int]]:
active_validators = get_active_validator_indices(validators)
shuffled_active_validator_indices = shuffle(active_validators, seed)
return split(shuffled_active_validator_indices, SHARD_COUNT)
```
We also define two functions for retrieving data from the state:
```python
@ -486,6 +490,8 @@ def add_validator_set_change_record(crystallized_state: CrystallizedState,
bytes1(flag) + bytes3(index) + bytes32(pubkey))
```
We define another set of helpers: `bytes1(x): return x.to_bytes(1, 'big')`, `bytes2(x): return x.to_bytes(2, 'big')`, and so on for all integers, particularly 1, 2, 3, 4, 8, 32.
Finally, we abstractly define `int_sqrt(n)` for use in reward/penalty calculations as the largest integer `k` such that `k**2 <= n`. Here is one possible implementation, though clients are free to use their own including standard libraries for [integer square root](https://en.wikipedia.org/wiki/Integer_square_root) if available and meet the specification.
```python
@ -537,6 +543,8 @@ def on_startup(initial_validator_entries: List[Any]) -> Tuple[CrystallizedState,
last_justified_slot=0,
justified_streak=0,
shard_and_committee_for_slots=x + x,
persistent_shuffling=split(shuffle(validators, b'x\00'*32), SHARD_COUNT),
shard_reassignment_records=[],
deposits_penalized_in_period=[],
validator_set_delta_hash_chain=bytes([0] * 32), # stub
pre_fork_version=INITIAL_FORK_VERSION,
@ -810,17 +818,12 @@ def change_validators(validators: List[ValidatorRecord]) -> None:
For any validator that was added or removed from the active validator list during this state recalculation:
* If the validator was removed, remove their index from the `current_persistent_committees` and `next_persistent_committees` objects.
* If the validator was removed, remove their index from the `persistent_committees` and `next_persistent_committees` objects.
* If the validator was added with index `validator_index`, let `assigned_shard = hash(active_state.randao_mix + bytes8(validator_index)) % SHARD_COUNT`. Add `validator_index` to the end of `next_persistent_committees[assigned_shard]`.
If `block.slot % SHARD_PERSISTENT_COMMITTEE_CHANGE_PERIOD == 0`, then:
* Set `current_persistent_committees = next_persistent_committees`
* Set `next_persistent_committees = get_persistent_shuffling(validators, active_state.randao_mix)`
```
### Possible alternative (run every state recalculation):
Now run the following code to reshuffle a few proposers:
```python
active_validator_indices = get_active_validator_indices(validators)
for i in range(len(active_validator_indices) // SHARD_PERSISTENT_COMMITTEE_CHANGE_PERIOD):
vid = active_validator_indices[hash(active_state.randao_mix + bytes8(i * 2)) % len(active_validator_indices)]
@ -829,10 +832,10 @@ for i in range(len(active_validator_indices) // SHARD_PERSISTENT_COMMITTEE_CHANG
while len(crystallized_state.persistent_shard_reassignments) > 0 and crystallized_state.persistent_shard_reassignments[0].slot <= block.slot:
rec = crystallized_state.persistent_shard_reassignments[0]
for c in crystallized_state.current_persistent_committees:
for c in crystallized_state.persistent_committees:
if rec.validator_id in c:
c.pop(c.index(rec.validator_id))
crystallized_state.current_persistent_committees[rec.shard].append(vid)
crystallized_state.persistent_committees[rec.shard].append(vid)
```
### TODO