mirror of
https://gitlab.com/pulsechaincom/prysm-pulse.git
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611 lines
22 KiB
Go
611 lines
22 KiB
Go
// Package helpers contains helper functions outlined in ETH2.0 spec:
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// https://github.com/ethereum/eth2.0-specs/blob/master/specs/core/0_beacon-chain.md#helper-functions
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package helpers
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import (
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"encoding/binary"
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"errors"
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"fmt"
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"github.com/prysmaticlabs/prysm/beacon-chain/utils"
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pb "github.com/prysmaticlabs/prysm/proto/beacon/p2p/v1"
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"github.com/prysmaticlabs/prysm/shared/bitutil"
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"github.com/prysmaticlabs/prysm/shared/bytesutil"
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"github.com/prysmaticlabs/prysm/shared/mathutil"
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"github.com/prysmaticlabs/prysm/shared/params"
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"google.golang.org/grpc/codes"
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"google.golang.org/grpc/status"
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)
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// CrosslinkCommittee defines the validator committee of slot and shard combinations.
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type CrosslinkCommittee struct {
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Committee []uint64
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Shard uint64
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}
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type shufflingInput struct {
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seed []byte
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shufflingEpoch uint64
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slot uint64
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startShard uint64
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committeesPerEpoch uint64
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}
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// EpochCommitteeCount returns the number of crosslink committees of an epoch.
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//
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// Spec pseudocode definition:
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// def get_epoch_committee_count(active_validator_count: int) -> int:
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// """
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// Return the number of committees in one epoch.
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// """
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// return max(
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// 1,
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// min(
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// SHARD_COUNT // SLOTS_PER_EPOCH,
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// active_validator_count // SLOTS_PER_EPOCH // TARGET_COMMITTEE_SIZE,
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// )
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// ) * SLOTS_PER_EPOCH
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func EpochCommitteeCount(activeValidatorCount uint64) uint64 {
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var minCommitteePerSlot = uint64(1)
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// Max committee count per slot will be 0 when shard count is less than epoch length, this
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// covers the special case to ensure there's always 1 max committee count per slot.
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var maxCommitteePerSlot = minCommitteePerSlot
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if params.BeaconConfig().ShardCount/params.BeaconConfig().SlotsPerEpoch > minCommitteePerSlot {
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maxCommitteePerSlot = params.BeaconConfig().ShardCount / params.BeaconConfig().SlotsPerEpoch
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}
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var currCommitteePerSlot = activeValidatorCount / params.BeaconConfig().SlotsPerEpoch / params.BeaconConfig().TargetCommitteeSize
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if currCommitteePerSlot > maxCommitteePerSlot {
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return maxCommitteePerSlot * params.BeaconConfig().SlotsPerEpoch
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}
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if currCommitteePerSlot < 1 {
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return minCommitteePerSlot * params.BeaconConfig().SlotsPerEpoch
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}
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return currCommitteePerSlot * params.BeaconConfig().SlotsPerEpoch
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}
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// CurrentEpochCommitteeCount returns the number of crosslink committees per epoch
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// of the current epoch.
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// Ex: Returns 100 means there's 8 committees assigned to current epoch.
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//
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// Spec pseudocode definition:
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// def get_current_epoch_committee_count(state: BeaconState) -> int:
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// """
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// Return the number of committees in the current epoch of the given ``state``.
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// """
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// current_active_validators = get_active_validator_indices(
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// state.validator_registry,
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// get_current_epoch(state),
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// )
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// return get_epoch_committee_count(len(current_active_validators)
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func CurrentEpochCommitteeCount(state *pb.BeaconState) uint64 {
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currActiveValidatorIndices := ActiveValidatorIndices(
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state.ValidatorRegistry, CurrentEpoch(state))
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return EpochCommitteeCount(uint64(len(currActiveValidatorIndices)))
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}
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// PrevEpochCommitteeCount returns the number of committees per slot
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// of the previous epoch.
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//
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// Spec pseudocode definition:
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// def get_previous_epoch_committee_count(state: BeaconState) -> int:
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// """
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// Return the number of committees in the previous epoch of the given ``state``.
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// """
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// previous_active_validators = get_active_validator_indices(
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// state.validator_registry,
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// state.previous_epoch,
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// )
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// return get_epoch_committee_count(len(previous_active_validators))
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func PrevEpochCommitteeCount(state *pb.BeaconState) uint64 {
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prevActiveValidatorIndices := ActiveValidatorIndices(
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state.ValidatorRegistry, PrevEpoch(state))
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return EpochCommitteeCount(uint64(len(prevActiveValidatorIndices)))
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}
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// NextEpochCommitteeCount returns the number of committees per slot
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// of the next epoch.
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//
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// Spec pseudocode definition:
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// def get_next_epoch_committee_count(state: BeaconState) -> int:
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// """
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// Return the number of committees in the next epoch of the given ``state``.
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// """
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// next_active_validators = get_active_validator_indices(
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// state.validator_registry,
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// get_current_epoch(state) + 1,
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// )
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// return get_epoch_committee_count(len(next_active_validators))
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func NextEpochCommitteeCount(state *pb.BeaconState) uint64 {
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prevActiveValidatorIndices := ActiveValidatorIndices(
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state.ValidatorRegistry, CurrentEpoch(state)+1)
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return EpochCommitteeCount(uint64(len(prevActiveValidatorIndices)))
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}
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// CrosslinkCommitteesAtSlot returns the list of crosslink committees, it
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// contains the shard associated with the committee and the validator indices
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// in that committee.
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//
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// Spec pseudocode definition:
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// def get_crosslink_committees_at_slot(state: BeaconState,
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// slot: Slot,
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// registry_change: bool=False) -> List[Tuple[List[ValidatorIndex], Shard]]:
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// """
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// Return the list of ``(committee, shard)`` tuples for the ``slot``.
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//
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// Note: There are two possible shufflings for crosslink committees for a
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// ``slot`` in the next epoch -- with and without a `registry_change`
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// """
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// epoch = slot_to_epoch(slot)
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// current_epoch = get_current_epoch(state)
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// previous_epoch = get_previous_epoch(state)
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// next_epoch = current_epoch + 1
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//
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// assert previous_epoch <= epoch <= next_epoch
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//
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// if epoch == current_epoch:
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// return get_current_epoch_committees_at_slot(state, slot)
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// elif epoch == previous_epoch:
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// return get_previous_epoch_committees_at_slot(state, slot)
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// elif epoch == next_epoch:
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// return get_next_epoch_committee_count(state, slot, registry_change)
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func CrosslinkCommitteesAtSlot(
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state *pb.BeaconState,
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slot uint64,
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registryChange bool) ([]*CrosslinkCommittee, error) {
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wantedEpoch := SlotToEpoch(slot)
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currentEpoch := CurrentEpoch(state)
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prevEpoch := PrevEpoch(state)
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nextEpoch := NextEpoch(state)
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switch wantedEpoch {
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case currentEpoch:
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return currEpochCommitteesAtSlot(state, slot)
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case prevEpoch:
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return prevEpochCommitteesAtSlot(state, slot)
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case nextEpoch:
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return nextEpochCommitteesAtSlot(state, slot, registryChange)
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default:
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return nil, fmt.Errorf(
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"input committee epoch %d out of bounds: %d <= epoch <= %d",
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wantedEpoch-params.BeaconConfig().GenesisEpoch,
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prevEpoch-params.BeaconConfig().GenesisEpoch,
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currentEpoch-params.BeaconConfig().GenesisEpoch,
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)
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}
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}
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// Shuffling shuffles input validator indices and splits them by slot and shard.
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//
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// Spec pseudocode definition:
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// def get_shuffling(seed: Bytes32,
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// validators: List[Validator],
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// epoch: Epoch) -> List[List[ValidatorIndex]]
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// """
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// Shuffle ``validators`` into crosslink committees seeded by ``seed`` and ``epoch``.
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// Return a list of ``committees_per_epoch`` committees where each
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// committee is itself a list of validator indices.
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// """
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//
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// active_validator_indices = get_active_validator_indices(validators, epoch)
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//
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// committees_per_epoch = get_epoch_committee_count(len(active_validator_indices))
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//
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// # Shuffle
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// seed = xor(seed, int_to_bytes32(epoch))
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// shuffled_active_validator_indices = shuffle(active_validator_indices, seed)
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//
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// # Split the shuffled list into committees_per_epoch pieces
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// return split(shuffled_active_validator_indices, committees_per_epoch)
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func Shuffling(
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seed [32]byte,
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validators []*pb.Validator,
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slot uint64) ([][]uint64, error) {
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// Normalize slot to start of epoch boundary.
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slot -= slot % params.BeaconConfig().SlotsPerEpoch
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// Figure out how many committees can be in a single slot.
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activeIndices := ActiveValidatorIndices(validators, slot)
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activeCount := uint64(len(activeIndices))
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committeesPerEpoch := EpochCommitteeCount(activeCount)
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// Convert slot to bytes and xor it with seed.
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slotInBytes := make([]byte, 32)
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binary.LittleEndian.PutUint64(slotInBytes, slot)
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seed = bytesutil.ToBytes32(bytesutil.Xor(seed[:], slotInBytes))
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shuffledIndices, err := utils.ShuffleIndices(seed, activeIndices)
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if err != nil {
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return nil, err
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}
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// Split the shuffled list into epoch_length * committees_per_slot pieces.
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return utils.SplitIndices(shuffledIndices, committeesPerEpoch), nil
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}
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// AttestationParticipants returns the attesting participants indices.
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//
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// Spec pseudocode definition:
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// def get_attestation_participants(state: BeaconState,
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// attestation_data: AttestationData,
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// bitfield: bytes) -> List[ValidatorIndex]:
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// """
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// Returns the participant indices at for the ``attestation_data`` and ``bitfield``.
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// """
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// # Find the committee in the list with the desired shard
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// crosslink_committees = get_crosslink_committees_at_slot(state, attestation_data.slot)
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//
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// assert attestation_data.shard in [shard for _, shard in crosslink_committees]
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// crosslink_committee = [committee for committee,
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// shard in crosslink_committees if shard == attestation_data.shard][0]
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//
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// assert verify_bitfield(bitfield, len(crosslink_committee))
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//
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// # Find the participating attesters in the committee
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// participants = []
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// for i, validator_index in enumerate(crosslink_committee):
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// aggregation_bit = get_bitfield_bit(bitfield, i)
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// if aggregation_bit == 0b1:
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// participants.append(validator_index)
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// return participants
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func AttestationParticipants(
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state *pb.BeaconState,
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attestationData *pb.AttestationData,
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bitfield []byte) ([]uint64, error) {
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// Find the relevant committee.
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// RegistryChange is a no-op when requesting slot in current and previous epoch.
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// AttestationParticipants is used to calculate justification and finality hence won't be used
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// to request crosslink commitees of future epoch.
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crosslinkCommittees, err := CrosslinkCommitteesAtSlot(state, attestationData.Slot, false /* registryChange */)
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if err != nil {
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return nil, err
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}
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var committee []uint64
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for _, crosslinkCommittee := range crosslinkCommittees {
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if crosslinkCommittee.Shard == attestationData.Shard {
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committee = crosslinkCommittee.Committee
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break
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}
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}
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if isValidated, err := VerifyBitfield(bitfield, len(committee)); !isValidated || err != nil {
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if err != nil {
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return nil, err
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}
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return nil, errors.New("bitfield is unable to be verified")
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}
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// Find the participating validators in the committee.
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var participants []uint64
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for i, validatorIndex := range committee {
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bitSet, err := bitutil.CheckBit(bitfield, i)
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if err != nil {
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return nil, fmt.Errorf("could not get participant bitfield: %v", err)
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}
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if bitSet {
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participants = append(participants, validatorIndex)
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}
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}
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return participants, nil
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}
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// VerifyBitfield validates a bitfield with a given committee size.
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//
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// Spec pseudocode:
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//
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// def verify_bitfield(bitfield: bytes, committee_size: int) -> bool:
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// """
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// Verify ``bitfield`` against the ``committee_size``.
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// """
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// if len(bitfield) != (committee_size + 7) // 8:
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// return False
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//
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// # Check `bitfield` is padded with zero bits only
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// for i in range(committee_size, len(bitfield) * 8):
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// if get_bitfield_bit(bitfield, i) == 0b1:
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// return False
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//
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// return True
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func VerifyBitfield(bitfield []byte, committeeSize int) (bool, error) {
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if len(bitfield) != mathutil.CeilDiv8(committeeSize) {
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return false, fmt.Errorf(
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"wanted participants bitfield length %d, got: %d",
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mathutil.CeilDiv8(committeeSize),
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len(bitfield))
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}
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for i := committeeSize; i < len(bitfield)*8; i++ {
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bitSet, err := bitutil.CheckBit(bitfield, i)
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if err != nil {
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return false, fmt.Errorf("unable to check bit in bitfield %v", err)
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}
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if bitSet {
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return false, nil
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}
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}
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return true, nil
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}
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// CommitteeAssignment is used to query committee assignment from
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// current and previous epoch.
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//
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// Spec pseudocode definition:
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// def get_committee_assignment(
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// state: BeaconState,
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// epoch: Epoch,
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// validator_index: ValidatorIndex,
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// registry_change: bool=False) -> Tuple[List[ValidatorIndex], Shard, Slot, bool]:
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// """
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// Return the committee assignment in the ``epoch`` for ``validator_index`` and ``registry_change``.
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// ``assignment`` returned is a tuple of the following form:
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// * ``assignment[0]`` is the list of validators in the committee
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// * ``assignment[1]`` is the shard to which the committee is assigned
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// * ``assignment[2]`` is the slot at which the committee is assigned
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// * ``assignment[3]`` is a bool signalling if the validator is expected to propose
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// a beacon block at the assigned slot.
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// """
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// previous_epoch = get_previous_epoch(state)
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// next_epoch = get_current_epoch(state)
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// assert previous_epoch <= epoch <= next_epoch
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//
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// epoch_start_slot = get_epoch_start_slot(epoch)
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// for slot in range(epoch_start_slot, epoch_start_slot + SLOTS_PER_EPOCH):
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// crosslink_committees = get_crosslink_committees_at_slot(
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// state,
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// slot,
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// registry_change=registry_change,
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// )
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// selected_committees = [
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// committee # Tuple[List[ValidatorIndex], Shard]
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// for committee in crosslink_committees
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// if validator_index in committee[0]
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// ]
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// if len(selected_committees) > 0:
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// validators = selected_committees[0][0]
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// shard = selected_committees[0][1]
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// first_committee_at_slot = crosslink_committees[0][0] # List[ValidatorIndex]
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// is_proposer = first_committee_at_slot[slot % len(first_committee_at_slot)] == validator_index
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//
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// assignment = (validators, shard, slot, is_proposer)
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// return assignment
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func CommitteeAssignment(
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state *pb.BeaconState,
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slot uint64,
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validatorIndex uint64,
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registryChange bool) ([]uint64, uint64, uint64, bool, error) {
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var selectedCommittees []*CrosslinkCommittee
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wantedEpoch := slot / params.BeaconConfig().SlotsPerEpoch
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prevEpoch := PrevEpoch(state)
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nextEpoch := NextEpoch(state)
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if wantedEpoch < prevEpoch || wantedEpoch > nextEpoch {
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return nil, 0, 0, false, fmt.Errorf(
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"epoch %d out of bounds: %d <= epoch <= %d",
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wantedEpoch-params.BeaconConfig().GenesisEpoch,
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prevEpoch-params.BeaconConfig().GenesisEpoch,
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nextEpoch-params.BeaconConfig().GenesisEpoch,
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)
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}
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startSlot := StartSlot(wantedEpoch)
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for slot := startSlot; slot < startSlot+params.BeaconConfig().SlotsPerEpoch; slot++ {
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crosslinkCommittees, err := CrosslinkCommitteesAtSlot(
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state, slot, registryChange)
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if err != nil {
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return []uint64{}, 0, 0, false, fmt.Errorf("could not get crosslink committee: %v", err)
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}
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for _, committee := range crosslinkCommittees {
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for _, idx := range committee.Committee {
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if idx == validatorIndex {
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selectedCommittees = append(selectedCommittees, committee)
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}
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if len(selectedCommittees) > 0 {
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validators := selectedCommittees[0].Committee
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shard := selectedCommittees[0].Shard
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firstCommitteeAtSlot := crosslinkCommittees[0].Committee
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isProposer := firstCommitteeAtSlot[slot%
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uint64(len(firstCommitteeAtSlot))] == validatorIndex
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return validators, shard, slot, isProposer, nil
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}
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}
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}
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}
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return []uint64{}, 0, 0, false, status.Error(codes.NotFound, "validator not found found in assignments")
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}
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// prevEpochCommitteesAtSlot returns a list of crosslink committees of the previous epoch.
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//
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// Spec pseudocode definition:
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// def get_previous_epoch_committees_at_slot(state: BeaconState,
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// slot: Slot) -> List[Tuple[List[ValidatorIndex], Shard]]:
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// committees_per_epoch = get_previous_epoch_committee_count(state)
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// seed = state.previous_shuffling_seed
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// shuffling_epoch = state.previous_shuffling_epoch
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// shuffling_start_shard = state.previous_shuffling_start_shard
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// return get_crosslink_committees(
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// state,
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// seed,
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// shuffling_epoch,
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// slot,
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// start_shard,
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// committees_per_epoch,
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// )
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func prevEpochCommitteesAtSlot(state *pb.BeaconState, slot uint64) ([]*CrosslinkCommittee, error) {
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committeesPerEpoch := PrevEpochCommitteeCount(state)
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return crosslinkCommittees(
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state, &shufflingInput{
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seed: state.PreviousShufflingSeedHash32,
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shufflingEpoch: state.PreviousShufflingEpoch,
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slot: slot,
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startShard: state.PreviousShufflingStartShard,
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committeesPerEpoch: committeesPerEpoch,
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})
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}
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// currEpochCommitteesAtSlot returns a list of crosslink committees of the current epoch.
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//
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// Spec pseudocode definition:
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// def get_current_epoch_committees_at_slot(state: BeaconState,
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// slot: Slot) -> List[Tuple[List[ValidatorIndex], Shard]]:
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// committees_per_epoch = get_current_epoch_committee_count(state)
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// seed = state.current_shuffling_seed
|
|
// shuffling_epoch = state.current_shuffling_epoch
|
|
// shuffling_start_shard = state.current_shuffling_start_shard
|
|
// return get_crosslink_committees(
|
|
// state,
|
|
// seed,
|
|
// shuffling_epoch,
|
|
// slot,
|
|
// start_shard,
|
|
// committees_per_epoch,
|
|
// )
|
|
func currEpochCommitteesAtSlot(state *pb.BeaconState, slot uint64) ([]*CrosslinkCommittee, error) {
|
|
committeesPerEpoch := CurrentEpochCommitteeCount(state)
|
|
return crosslinkCommittees(
|
|
state, &shufflingInput{
|
|
seed: state.CurrentShufflingSeedHash32,
|
|
shufflingEpoch: state.CurrentShufflingEpoch,
|
|
slot: slot,
|
|
startShard: state.CurrentShufflingStartShard,
|
|
committeesPerEpoch: committeesPerEpoch,
|
|
})
|
|
}
|
|
|
|
// nextEpochCommitteesAtSlot returns a list of crosslink committees of the next epoch.
|
|
//
|
|
// Spec pseudocode definition:
|
|
// def get_next_epoch_committees_at_slot(state: BeaconState,
|
|
// slot: Slot,
|
|
// registry_change: bool) -> List[Tuple[List[ValidatorIndex], Shard]]:
|
|
// epochs_since_last_registry_update = current_epoch - state.validator_registry_update_epoch
|
|
// if registry_change:
|
|
// committees_per_epoch = get_next_epoch_committee_count(state)
|
|
// seed = generate_seed(state, next_epoch)
|
|
// shuffling_epoch = next_epoch
|
|
// current_committees_per_epoch = get_current_epoch_committee_count(state)
|
|
// shuffling_start_shard = (state.current_shuffling_start_shard + current_committees_per_epoch) % SHARD_COUNT
|
|
// elif epochs_since_last_registry_update > 1 and is_power_of_two(epochs_since_last_registry_update):
|
|
// committees_per_epoch = get_next_epoch_committee_count(state)
|
|
// seed = generate_seed(state, next_epoch)
|
|
// shuffling_epoch = next_epoch
|
|
// shuffling_start_shard = state.current_shuffling_start_shard
|
|
// else:
|
|
// committees_per_epoch = get_current_epoch_committee_count(state)
|
|
// seed = state.current_shuffling_seed
|
|
// shuffling_epoch = state.current_shuffling_epoch
|
|
// shuffling_start_shard = state.current_shuffling_start_shard
|
|
//
|
|
// return get_crosslink_committees(
|
|
// state,
|
|
// seed,
|
|
// shuffling_epoch,
|
|
// slot,
|
|
// start_shard,
|
|
// committees_per_epoch,
|
|
// )
|
|
func nextEpochCommitteesAtSlot(state *pb.BeaconState, slot uint64, registryChange bool) ([]*CrosslinkCommittee, error) {
|
|
var committeesPerEpoch uint64
|
|
var shufflingEpoch uint64
|
|
var shufflingStartShard uint64
|
|
var seed [32]byte
|
|
var err error
|
|
|
|
epochsSinceLastUpdate := CurrentEpoch(state) - state.ValidatorRegistryUpdateEpoch
|
|
if registryChange {
|
|
committeesPerEpoch = NextEpochCommitteeCount(state)
|
|
shufflingEpoch = NextEpoch(state)
|
|
seed, err = GenerateSeed(state, shufflingEpoch)
|
|
if err != nil {
|
|
return nil, fmt.Errorf("could not generate seed: %v", err)
|
|
}
|
|
shufflingStartShard = (state.CurrentShufflingStartShard + CurrentEpochCommitteeCount(state)) %
|
|
params.BeaconConfig().ShardCount
|
|
} else if epochsSinceLastUpdate > 1 &&
|
|
mathutil.IsPowerOf2(epochsSinceLastUpdate) {
|
|
committeesPerEpoch = NextEpochCommitteeCount(state)
|
|
shufflingEpoch = NextEpoch(state)
|
|
seed, err = GenerateSeed(state, shufflingEpoch)
|
|
if err != nil {
|
|
return nil, fmt.Errorf("could not generate seed: %v", err)
|
|
}
|
|
shufflingStartShard = state.CurrentShufflingStartShard
|
|
} else {
|
|
committeesPerEpoch = CurrentEpochCommitteeCount(state)
|
|
seed = bytesutil.ToBytes32(state.CurrentShufflingSeedHash32)
|
|
shufflingEpoch = state.CurrentShufflingEpoch
|
|
shufflingStartShard = state.CurrentShufflingStartShard
|
|
}
|
|
|
|
return crosslinkCommittees(
|
|
state, &shufflingInput{
|
|
seed: seed[:],
|
|
shufflingEpoch: shufflingEpoch,
|
|
slot: slot,
|
|
startShard: shufflingStartShard,
|
|
committeesPerEpoch: committeesPerEpoch,
|
|
})
|
|
}
|
|
|
|
// crosslinkCommittees breaks down the shuffled indices into list of crosslink committee structs
|
|
// which contains of validator indices and the shard they are assigned to.
|
|
//
|
|
// Spec pseudocode definition:
|
|
// def get_crosslink_committees(state: BeaconState,
|
|
// seed: Bytes32,
|
|
// shuffling_epoch: Epoch,
|
|
// slot: Slot,
|
|
// start_shard: Shard,
|
|
// committees_per_epoch: int) -> List[Tuple[List[ValidatorIndex], Shard]]:
|
|
// offset = slot % SLOTS_PER_EPOCH
|
|
// committees_per_slot = committees_per_epoch // SLOTS_PER_EPOCH
|
|
// slot_start_shard = (shuffling_start_shard + committees_per_slot * offset) % SHARD_COUNT
|
|
//
|
|
// shuffling = get_shuffling(
|
|
// seed,
|
|
// state.validator_registry,
|
|
// shuffling_epoch,
|
|
// )
|
|
//
|
|
// return [
|
|
// (
|
|
// shuffling[committees_per_slot * offset + i],
|
|
// (slot_start_shard + i) % SHARD_COUNT,
|
|
// )
|
|
// for i in range(committees_per_slot)
|
|
// ]
|
|
func crosslinkCommittees(state *pb.BeaconState, input *shufflingInput) ([]*CrosslinkCommittee, error) {
|
|
slotsPerEpoch := params.BeaconConfig().SlotsPerEpoch
|
|
offSet := input.slot % slotsPerEpoch
|
|
committeesPerSlot := input.committeesPerEpoch / slotsPerEpoch
|
|
slotStartShard := (input.startShard + committeesPerSlot*offSet) %
|
|
params.BeaconConfig().ShardCount
|
|
|
|
shuffledIndices, err := Shuffling(
|
|
bytesutil.ToBytes32(input.seed),
|
|
state.ValidatorRegistry,
|
|
input.shufflingEpoch)
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
|
|
var crosslinkCommittees []*CrosslinkCommittee
|
|
for i := uint64(0); i < committeesPerSlot; i++ {
|
|
crosslinkCommittees = append(crosslinkCommittees, &CrosslinkCommittee{
|
|
Committee: shuffledIndices[committeesPerSlot*offSet+i],
|
|
Shard: (slotStartShard + i) % params.BeaconConfig().ShardCount,
|
|
})
|
|
}
|
|
return crosslinkCommittees, nil
|
|
}
|