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Merge pull request #1714 from ethereum/hwwhww/validator_index 

Strict `ValidatorIndex` definition
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Danny Ryan 2020-04-14 11:52:41 -06:00 committed by GitHub
parent 2a36f366ef b2f6325db3
commit 1e9df66fba
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specs/phase0/beacon-chain.md
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@ -722,9 +722,9 @@ def is_valid_merkle_branch(leaf: Bytes32, branch: Sequence[Bytes32], depth: uint
#### `compute_shuffled_index` #### `compute_shuffled_index`
```python ```python
def compute_shuffled_index(index: ValidatorIndex, index_count: uint64, seed: Bytes32) -> ValidatorIndex: def compute_shuffled_index(index: uint64, index_count: uint64, seed: Bytes32) -> uint64:
""" """
Return the shuffled validator index corresponding to ``seed`` (and ``index_count``). Return the shuffled index corresponding to ``seed`` (and ``index_count``).
""" """
assert index < index_count assert index < index_count
@ -732,14 +732,14 @@ def compute_shuffled_index(index: ValidatorIndex, index_count: uint64, seed: Byt
# See the 'generalized domain' algorithm on page 3 # See the 'generalized domain' algorithm on page 3
for current_round in range(SHUFFLE_ROUND_COUNT): for current_round in range(SHUFFLE_ROUND_COUNT):
pivot = bytes_to_int(hash(seed + int_to_bytes(current_round, length=1))[0:8]) % index_count pivot = bytes_to_int(hash(seed + int_to_bytes(current_round, length=1))[0:8]) % index_count
flip = ValidatorIndex((pivot + index_count - index) % index_count) flip = (pivot + index_count - index) % index_count
position = max(index, flip) position = max(index, flip)
source = hash(seed + int_to_bytes(current_round, length=1) + int_to_bytes(position // 256, length=4)) source = hash(seed + int_to_bytes(current_round, length=1) + int_to_bytes(position // 256, length=4))
byte = source[(position % 256) // 8] byte = source[(position % 256) // 8]
bit = (byte >> (position % 8)) % 2 bit = (byte >> (position % 8)) % 2
index = flip if bit else index index = flip if bit else index
return ValidatorIndex(index) return index
``` ```
#### `compute_proposer_index` #### `compute_proposer_index`
@ -753,11 +753,11 @@ def compute_proposer_index(state: BeaconState, indices: Sequence[ValidatorIndex]
MAX_RANDOM_BYTE = 2**8 - 1 MAX_RANDOM_BYTE = 2**8 - 1
i = 0 i = 0
while True: while True:
candidate_index = indices[compute_shuffled_index(ValidatorIndex(i % len(indices)), len(indices), seed)] candidate_index = indices[compute_shuffled_index(i % len(indices), len(indices), seed)]
random_byte = hash(seed + int_to_bytes(i // 32, length=8))[i % 32] random_byte = hash(seed + int_to_bytes(i // 32, length=8))[i % 32]
effective_balance = state.validators[candidate_index].effective_balance effective_balance = state.validators[candidate_index].effective_balance
if effective_balance * MAX_RANDOM_BYTE >= MAX_EFFECTIVE_BALANCE * random_byte: if effective_balance * MAX_RANDOM_BYTE >= MAX_EFFECTIVE_BALANCE * random_byte:
return ValidatorIndex(candidate_index) return candidate_index
i += 1 i += 1
``` ```
@ -773,7 +773,7 @@ def compute_committee(indices: Sequence[ValidatorIndex],
""" """
start = (len(indices) * index) // count start = (len(indices) * index) // count
end = (len(indices) * (index + 1)) // count end = (len(indices) * (index + 1)) // count
return [indices[compute_shuffled_index(ValidatorIndex(i), len(indices), seed)] for i in range(start, end)] return [indices[compute_shuffled_index(i, len(indices), seed)] for i in range(start, end)]
``` ```
#### `compute_epoch_at_slot` #### `compute_epoch_at_slot`