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https://github.com/status-im/nimbus-eth2.git
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Depart from spec "attestation_targets"
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mratsim
zah
parent
4a6e694268
commit
f0e3de6b19
@ -1,8 +1,8 @@
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import
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deques, options,
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milagro_crypto,
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./spec/[datatypes, crypto, digest, helpers], extras,
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tables, hashes # For BeaconChainDB stub
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./spec/[datatypes, crypto, digest, helpers, validator], extras,
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tables, hashes
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type
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AttestationCandidate* = object
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@ -91,9 +91,6 @@ proc add*(pool: var AttestationPool,
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pool.attestations.setLen(slotIdxInPool + 1)
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let shard = attestation.data.shard
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if attestation.data.slot.int > pool.highestSlot:
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pool.highestSlot = attestation.data.slot.int
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pool.highestSlotAttestationShard = shard.int
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if pool.attestations[slotIdxInPool][shard].isSome:
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combine(pool.attestations[slotIdxInPool][shard].get, attestation, {})
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@ -138,28 +135,68 @@ func getAttestationCandidate*(attestation: Attestation): AttestationCandidate =
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# ##################################################################
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# Specs
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#
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# The beacon chain fork choice rule is a hybrid that combines justification and finality with Latest Message Driven (LMD) Greediest Heaviest Observed SubTree (GHOST). At any point in time a [validator](#dfn-validator) `v` subjectively calculates the beacon chain head as follows.
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#
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# * Let `store` be the set of attestations and blocks
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# that the validator `v` has observed and verified
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# (in particular, block ancestors must be recursively verified).
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# Attestations not part of any chain are still included in `store`.
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# * Let `finalized_head` be the finalized block with the highest slot number.
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# (A block `B` is finalized if there is a descendant of `B` in `store`
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# the processing of which sets `B` as finalized.)
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# * Let `justified_head` be the descendant of `finalized_head`
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# with the highest slot number that has been justified
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# for at least `EPOCH_LENGTH` slots.
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# (A block `B` is justified if there is a descendant of `B` in `store`
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# the processing of which sets `B` as justified.)
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# If no such descendant exists set `justified_head` to `finalized_head`.
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# * Let `get_ancestor(store, block, slot)` be the ancestor of `block` with slot number `slot`.
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# The `get_ancestor` function can be defined recursively
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#
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# def get_ancestor(store, block, slot):
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# return block if block.slot == slot
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# else get_ancestor(store, store.get_parent(block), slot)`.
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#
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# * Let `get_latest_attestation(store, validator)`
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# be the attestation with the highest slot number in `store` from `validator`.
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# If several such attestations exist,
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# use the one the validator `v` observed first.
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# * Let `get_latest_attestation_target(store, validator)`
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# be the target block in the attestation `get_latest_attestation(store, validator)`.
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# * The head is `lmd_ghost(store, justified_head)`. (See specs)
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#
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# Departing from specs:
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# - We use a simple fork choice rule without finalized and justified head
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# - We don't implement "get_latest_attestation(store, validator) -> Attestation"
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# nor get_latest_attestation_target
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func getLatestAttestation*(pool: AttestationPool): AttestationData =
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## Search for the attestation with the highest slot number
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## If multiple attestation have the same slot number, keep the first one.
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#
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# AttestationPool contains the attestations observed and verified
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# by the current client. (It might miss some).
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#
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# Difference with the spec
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# - Contrary to the spec we don't use "validator" as an input.
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# Specs assume that there is a global "Store" that keeps track of all attestations
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# observed by each invidual client.
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# AttestationPool only tracks attestations observed by the current client.
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func getVoteCount(participation_bitfield: openarray[byte]): int =
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## Get the number of votes
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# TODO: A bitfield type that tracks that information
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# https://github.com/status-im/nim-beacon-chain/issues/19
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var idx = pool.attestations.len - 1
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# Within a shard we can receive several attestations for the highest slot.
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while pool.attestations[idx][pool.highestSlotAttestationShard].get.data.slot.int == pool.highestSlot:
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idx -= 1
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result = pool.attestations[idx][pool.highestSlotAttestationShard].get.data
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for validatorIdx in 0 ..< participation_bitfield.len * 8:
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result += int participation_bitfield.bitIsSet(validatorIdx)
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func getLatestAttestationTarget*(pool: AttestationPool): Eth2Digest =
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pool.getLatestAttestation.beacon_block_root
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func getAttestationVoteCount(pool: AttestationPool, state: BeaconState): CountTable[BlockHash] =
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## Returns all blocks that were attested and their vote count for a specific slot.
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# This replaces:
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# - get_latest_attestation,
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# - get_latest_attestation_targets
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# that are used in lmd_ghost for
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# ```
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# attestation_targets = [get_latest_attestation_target(store, validator)
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# for validator in active_validators]
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# ```
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# Note that attestation_targets in the Eth2 specs can have duplicates
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# while the following implementation will count such blockhash multiple times instead.
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result = initCountTable[BlockHash]()
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for attestation in pool.attestations[state.slot.int - pool.startingSlot]:
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if attestation.isSome:
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# Increase the block attestation counts by the number of validators aggregated
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let voteCount = attestation.get.participation_bitfield.getVoteCount()
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result.inc(attestation.get.data.beacon_block_root, voteCount)
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func getParent(db: BeaconChainDB, blck: BeaconBlock): BeaconBlock =
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db.blocks[blck.parent_root]
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@ -172,8 +209,11 @@ func get_ancestor(store: BeaconChainDB, blck: BeaconBlock, slot: uint64): Beacon
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return store.get_ancestor(store.get_parent(blck), slot)
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# TODO: what if the slot was never observed/verified?
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func lmdGhost*(store: BeaconChainDB, pool: AttestationPool, start: BeaconBlock): BeaconBlock =
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func lmdGhost*(store: BeaconChainDB, pool: AttestationPool, state: BeaconState): BeaconBlock =
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# Recompute the new head of the beacon chain according to
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# LMD GHOST (Latest Message Driven - Greediest Heaviest Observed SubTree)
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discard
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let validators = state.validator_registry
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var active_validators: seq[ValidatorRecord]
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for i in validators.get_active_validator_indices:
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active_validators.add validators[i]
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