def get_new_shuffling(
*, seed: Hash32, validators: Sequence['ValidatorRecord'], dynasty: int,
crosslinking_start_shard: int, cycle_length: int,
min_committee_size: int,
shard_count: int) -> Iterable[Iterable[ShardAndCommittee]]:
"""
Returns shuffled ``shard_and_committee_for_slots`` (``[[ShardAndCommittee]]``) of
the given active ``validators``.
Two-dimensional:
The first layer is ``slot`` number
``shard_and_committee_for_slots[slot] -> [ShardAndCommittee]``
The second layer is ``shard_indices`` number
``shard_and_committee_for_slots[slot][shard_indices] -> ShardAndCommittee``
Example:
validators:
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15]
After shuffling:
[6, 0, 2, 12, 14, 8, 10, 4, 9, 1, 5, 13, 15, 7, 3, 11]
Split by slot:
[
[6, 0, 2, 12, 14], [8, 10, 4, 9, 1], [5, 13, 15, 7, 3, 11]
]
Split by shard:
[
[6, 0], [2, 12, 14], [8, 10], [4, 9, 1], [5, 13, 15] ,[7, 3, 11]
]
Fill to output:
[
# slot 0
[
ShardAndCommittee(shard_id=0, committee=[6, 0]),
ShardAndCommittee(shard_id=1, committee=[2, 12, 14]),
],
# slot 1
[
ShardAndCommittee(shard_id=2, committee=[8, 10]),
ShardAndCommittee(shard_id=3, committee=[4, 9, 1]),
],
# slot 2
[
ShardAndCommittee(shard_id=4, committee=[5, 13, 15]),
ShardAndCommittee(shard_id=5, committee=[7, 3, 11]),
],
]
NOTE: The spec might be updated to output an array rather than an array of arrays.
"""
active_validators = get_active_validator_indices(dynasty, validators)
active_validators_size = len(active_validators)
committees_per_slot, slots_per_committee = _get_shuffling_committee_slot_portions(
active_validators_size,
cycle_length,
min_committee_size,
shard_count,
)
shuffled_active_validator_indices = shuffle(active_validators, seed)
# Split the shuffled list into cycle_length pieces
validators_per_slot = split(shuffled_active_validator_indices,
cycle_length)
for slot, slot_indices in enumerate(validators_per_slot):
# Split the shuffled list into committees_per_slot pieces
shard_indices = split(slot_indices, committees_per_slot)
shard_id_start = crosslinking_start_shard + (
slot * committees_per_slot // slots_per_committee)
yield _get_shards_and_committees_for_shard_indices(
shard_indices,
shard_id_start,
shard_count,
)
def test_shuffle_consistent(values, seed, expect):
assert shuffle(values, seed) == expect
def test_shuffle_out_of_bound():
values = [i for i in range(2**24 + 1)]
with pytest.raises(ValueError):
shuffle(values, b'hello')
def get_new_shuffling(*, seed: Hash32, validators: Sequence['ValidatorRecord'],
crosslinking_start_shard: int, epoch_length: int,
target_committee_size: int,
shard_count: int) -> Iterable[Iterable[ShardCommittee]]:
"""
Return shuffled ``shard_committee_for_slots`` (``[[ShardCommittee]]``) of
the given active ``validators`` using ``seed`` as entropy.
Two-dimensional:
The first layer is ``slot`` number
``shard_committee_for_slots[slot] -> [ShardCommittee]``
The second layer is ``shard_indices`` number
``shard_committee_for_slots[slot][shard_indices] -> ShardCommittee``
Example:
validators:
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15]
After shuffling:
[6, 0, 2, 12, 14, 8, 10, 4, 9, 1, 5, 13, 15, 7, 3, 11]
Split by slot:
[
[6, 0, 2, 12, 14], [8, 10, 4, 9, 1], [5, 13, 15, 7, 3, 11]
]
Split by shard:
[
[6, 0], [2, 12, 14], [8, 10], [4, 9, 1], [5, 13, 15] ,[7, 3, 11]
]
Fill to output:
[
# slot 0
[
ShardCommittee(shard_id=0, committee=[6, 0]),
ShardCommittee(shard_id=1, committee=[2, 12, 14]),
],
# slot 1
[
ShardCommittee(shard_id=2, committee=[8, 10]),
ShardCommittee(shard_id=3, committee=[4, 9, 1]),
],
# slot 2
[
ShardCommittee(shard_id=4, committee=[5, 13, 15]),
ShardCommittee(shard_id=5, committee=[7, 3, 11]),
],
]
"""
active_validators = get_active_validator_indices(validators)
active_validators_size = len(active_validators)
committees_per_slot = clamp(
1,
shard_count // epoch_length,
active_validators_size // epoch_length // target_committee_size,
)
# Shuffle with seed
shuffled_active_validator_indices = shuffle(active_validators, seed)
# Split the shuffled list into epoch_length pieces
validators_per_slot = split(shuffled_active_validator_indices,
epoch_length)
for index, slot_indices in enumerate(validators_per_slot):
# Split the shuffled list into committees_per_slot pieces
shard_indices = split(slot_indices, committees_per_slot)
start_shard = crosslinking_start_shard + index * committees_per_slot
yield _get_shards_committees_for_shard_indices(
shard_indices,
start_shard,
active_validators_size,
shard_count,
)