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consider per-slot sample target adjustment, to avoid racing and ordering problems

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protolambda 2021-07-26 16:27:19 +02:00
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1 changed files with 17 additions and 26 deletions
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specs/sharding/beacon-chain.md
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@ -441,7 +441,8 @@ def compute_previous_slot(slot: Slot) -> Slot:
#### `compute_updated_sample_price` #### `compute_updated_sample_price`
```python ```python
def compute_updated_sample_price(prev_price: Gwei, samples: uint64, adjustment_quotient: uint64) -> Gwei: def compute_updated_sample_price(prev_price: Gwei, samples: uint64, active_shards: uint64) -> Gwei:
adjustment_quotient = active_shards * SLOTS_PER_EPOCH * SAMPLE_PRICE_ADJUSTMENT_COEFFICIENT
if samples > TARGET_SAMPLES_PER_BLOB: if samples > TARGET_SAMPLES_PER_BLOB:
delta = max(1, prev_price * (samples - TARGET_SAMPLES_PER_BLOB) // TARGET_SAMPLES_PER_BLOB // adjustment_quotient) delta = max(1, prev_price * (samples - TARGET_SAMPLES_PER_BLOB) // TARGET_SAMPLES_PER_BLOB // adjustment_quotient)
return min(prev_price + delta, MAX_SAMPLE_PRICE) return min(prev_price + delta, MAX_SAMPLE_PRICE)
@ -578,19 +579,19 @@ def process_operations(state: BeaconState, body: BeaconBlockBody) -> None:
for_ops(body.attester_slashings, process_attester_slashing) for_ops(body.attester_slashings, process_attester_slashing)
# New shard proposer slashing processing # New shard proposer slashing processing
for_ops(body.shard_proposer_slashings, process_shard_proposer_slashing) for_ops(body.shard_proposer_slashings, process_shard_proposer_slashing)
# Limit is dynamic based on active shard count
# Limit is dynamic: based on active shard count
assert len(body.shard_headers) <= MAX_SHARD_HEADERS_PER_SHARD * get_active_shard_count(state, get_current_epoch(state)) assert len(body.shard_headers) <= MAX_SHARD_HEADERS_PER_SHARD * get_active_shard_count(state, get_current_epoch(state))
# Included shard headers must be sorted by shard index, the base-fee is adjusted in sequence (capacity is staggered)
# Duplicates (same slot and shard) are allowed, although slashable, only the first affects capacity.
if len(body.shard_headers) > 0:
shard = 0
for i, header in body.shard_headers[1:]
for_ops(body.shard_headers, process_shard_header) for_ops(body.shard_headers, process_shard_header)
# New attestation processing # New attestation processing
for_ops(body.attestations, process_attestation) for_ops(body.attestations, process_attestation)
for_ops(body.deposits, process_deposit) for_ops(body.deposits, process_deposit)
for_ops(body.voluntary_exits, process_voluntary_exit) for_ops(body.voluntary_exits, process_voluntary_exit)
# TODO: to avoid parallel shards racing, and avoid inclusion-order problems,
# update the fee price per slot, instead of per header.
# state.shard_sample_price = compute_updated_sample_price(state.shard_sample_price, ?, shard_count)
``` ```
##### Extended Attestation processing ##### Extended Attestation processing
@ -689,17 +690,15 @@ def process_shard_header(state: BeaconState, signed_header: SignedShardBlobHeade
header_epoch = compute_epoch_at_slot(slot) header_epoch = compute_epoch_at_slot(slot)
# Verify that the header is within the processing time window # Verify that the header is within the processing time window
assert header_epoch in [get_previous_epoch(state), get_current_epoch(state)] assert header_epoch in [get_previous_epoch(state), get_current_epoch(state)]
# Verify that the shard is active # Verify that the shard is valid
start_shard = get_start_shard(state, slot)
committees_per_slot = get_committee_count_per_slot(state, header_epoch)
end_shard = start_shard + committees_per_slot
shard_count = get_active_shard_count(state, header_epoch) shard_count = get_active_shard_count(state, header_epoch)
# Per slot, there may be max. shard_count committees. assert shard < shard_count
# If there are shard_count * 2/3 per slot, then wrap around. # Verify that a committee is able to attest this (slot, shard)
if end_shard >= shard_count: start_shard = get_start_shard(state, slot)
assert not (end_shard - shard_count <= shard < start_shard) committee_index = (shard_count + shard - start_shard) % shard_count
else: committees_per_slot = get_committee_count_per_slot(state, header_epoch)
assert start_shard <= shard < end_shard assert committee_index <= committees_per_slot
# Verify that the block root matches, # Verify that the block root matches,
# to ensure the header will only be included in this specific Beacon Chain sub-tree. # to ensure the header will only be included in this specific Beacon Chain sub-tree.
assert header.body_summary.beacon_block_root == get_block_root_at_slot(state, slot - 1) assert header.body_summary.beacon_block_root == get_block_root_at_slot(state, slot - 1)
@ -753,14 +752,6 @@ def process_shard_header(state: BeaconState, signed_header: SignedShardBlobHeade
# Pay out priority fee # Pay out priority fee
increase_balance(state, header.proposer_index, priority_fee) increase_balance(state, header.proposer_index, priority_fee)
# Track updated sample price
adjustment_quotient = (
get_active_shard_count(state, previous_epoch)
* SLOTS_PER_EPOCH * SAMPLE_PRICE_ADJUSTMENT_COEFFICIENT
)
state.shard_sample_price = compute_updated_sample_price(
state.shard_sample_price, blob_summary.commitment.length, adjustment_quotient)
# Initialize the pending header # Initialize the pending header
index = compute_committee_index_from_shard(state, slot, shard) index = compute_committee_index_from_shard(state, slot, shard)
committee_length = len(get_beacon_committee(state, slot, index)) committee_length = len(get_beacon_committee(state, slot, index))