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[squashed] shard chain updates wip 

Use `ShardBlock` in `shard_state_transition`

PR feedback

1. Rename `ShardState.data` -> `ShardState.transition_digest`
2. Rename `compute_shard_transition_data` to `compute_shard_transition_digest`
3. Add `assert state.slot > PHASE_1_GENESIS_SLOT` just in case, may move it later

Add `get_post_shard_state` as a pure function wrapper
This commit is contained in:
Hsiao-Wei Wang 2020-04-20 16:57:29 +08:00
parent 85d5a9abaf
commit 40483b587b
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GPG Key ID: 95B070122902DEA4
2 changed files with 40 additions and 26 deletions
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5
specs/phase1/beacon-chain.md
View File

@ -328,7 +328,7 @@ class ShardBlockHeader(Container):
class ShardState(Container):
slot: Slot
gasprice: Gwei
data: Bytes32
transition_digest: Bytes32
latest_block_root: Root
```
@ -701,6 +701,9 @@ def validate_attestation(state: BeaconState, attestation: Attestation) -> None:
```python
def apply_shard_transition(state: BeaconState, shard: Shard, transition: ShardTransition) -> None:
# TODO: only need to check it once when phase 1 starts
assert state.slot > PHASE_1_GENESIS_SLOT
# Correct data root count
offset_slots = get_offset_slots(state, shard)
assert (

61
specs/phase1/fraud-proofs.md
View File

@ -37,30 +37,43 @@ This document describes the shard transition function and fraud proofs as part o
```python
def shard_state_transition(beacon_state: BeaconState,
shard_state: ShardState,
signed_block: SignedShardBlock) -> None:
block: ShardBlock) -> None:
# Update shard state
prev_gasprice = shard_state.gasprice
if len(signed_block.message.body) == 0:
if len(block.body) == 0:
latest_block_root = shard_state.latest_block_root
else:
latest_block_root = hash_tree_root(signed_block.message)
latest_block_root = hash_tree_root(block)
shard_state.data = compute_shard_transition_data(
shard_state.transition_digest = compute_shard_transition_digest(
beacon_state,
shard_state,
signed_block.message.beacon_parent_root,
signed_block.message.body,
block.beacon_parent_root,
block.body,
)
shard_state.gasprice = compute_updated_gasprice(prev_gasprice, len(signed_block.message.body))
shard_state.slot = signed_block.message.slot
shard_state.gasprice = compute_updated_gasprice(prev_gasprice, len(block.body))
shard_state.slot = block.slot
shard_state.latest_block_root = latest_block_root
```
```python
def compute_shard_transition_data(beacon_state: BeaconState,
shard_state: ShardState,
beacon_parent_root: Root,
shard_body_root: Root) -> Bytes32:
def get_post_shard_state(beacon_state: BeaconState,
shard_state: ShardState,
block: ShardBlock) -> ShardState:
"""
A pure function that returns a new post ShardState instead of modifying the given `shard_state`.
"""
post_state = shard_state.copy()
shard_state_transition(beacon_state, post_state, block)
return post_state
```
```python
def compute_shard_transition_digest(beacon_state: BeaconState,
shard_state: ShardState,
beacon_parent_root: Root,
shard_body_root: Root) -> Bytes32:
# TODO: use SSZ hash tree root
return hash(
hash_tree_root(shard_state) + beacon_parent_root + shard_body_root
)
@ -107,25 +120,25 @@ def is_valid_fraud_proof(beacon_state: BeaconState,
attestation: Attestation,
offset_index: uint64,
transition: ShardTransition,
signed_block: SignedShardBlock,
block: ShardBlock,
subkey: BLSPubkey,
beacon_parent_block: BeaconBlock) -> bool:
# 1. Check if `custody_bits[offset_index][j] != generate_custody_bit(subkey, block_contents)` for any `j`.
shard = get_shard(beacon_state, attestation)
custody_bits = attestation.custody_bits_blocks
for j in range(custody_bits[offset_index]):
if custody_bits[offset_index][j] != generate_custody_bit(subkey, signed_block):
if custody_bits[offset_index][j] != generate_custody_bit(subkey, block):
return True
# 2. Check if the shard state transition result is wrong between
# `transition.shard_states[offset_index - 1]` to `transition.shard_states[offset_index]`.
if offset_index == 0:
shard_state = beacon_parent_block.shard_transitions[shard].shard_states[-1].copy()
shard_state = beacon_parent_block.shard_transitions[shard].shard_states[-1]
else:
shard_state = transition.shard_states[offset_index - 1].copy() # Not doing the actual state updates here.
shard_state = transition.shard_states[offset_index - 1] # Not doing the actual state updates here.
shard_state_transition(beacon_state, shard_state, signed_block)
if shard_state.data != transition.shard_states[offset_index].data:
shard_state = get_post_shard_state(beacon_state, shard_state, block)
if shard_state.transition_digest != transition.shard_states[offset_index].transition_digest:
return True
return False
@ -168,15 +181,14 @@ def get_proposal_choices_at_slot(beacon_state: BeaconState,
choices = []
shard_blocks_at_slot = [block for block in shard_blocks if block.message.slot == slot]
for block in shard_blocks_at_slot:
temp_shard_state = shard_state.copy() # Not doing the actual state updates here.
# Try to apply state transition to temp_shard_state.
try:
# Verify block message and signature
assert verify_shard_block_message(beacon_state, temp_shard_state, block.message, slot, shard)
# TODO these validations should have been checked upon receiving shard blocks.
assert verify_shard_block_message(beacon_state, shard_state, block.message, slot, shard)
if validate_signature:
assert verify_shard_block_signature(beacon_state, block)
shard_state_transition(beacon_state, temp_shard_state, block)
shard_state = get_post_shard_state(beacon_state, shard_state, block.message)
except Exception:
pass # TODO: throw error in the test helper
else:
@ -195,7 +207,6 @@ def get_proposal_at_slot(beacon_state: BeaconState,
Return ``proposal``, ``shard_state`` of the given ``slot``.
Note that this function doesn't change the state.
"""
shard_state = shard_state.copy() # Don't update the given shard_state
choices = get_proposal_choices_at_slot(
beacon_state=beacon_state,
shard_state=shard_state,
@ -213,7 +224,7 @@ def get_proposal_at_slot(beacon_state: BeaconState,
proposal = get_winning_proposal(beacon_state, choices)
# Apply state transition
shard_state_transition(beacon_state, shard_state, proposal)
shard_state = get_post_shard_state(beacon_state, shard_state, proposal.message)
return proposal, shard_state
```
@ -227,7 +238,7 @@ def get_shard_state_transition_result(
) -> Tuple[Sequence[SignedShardBlock], Sequence[ShardState], Sequence[Root]]:
proposals = []
shard_states = []
shard_state = beacon_state.shard_states[shard].copy()
shard_state = beacon_state.shard_states[shard]
for slot in get_offset_slots(beacon_state, shard):
proposal, shard_state = get_proposal_at_slot(
beacon_state=beacon_state,