mirror of
https://gitlab.com/pulsechaincom/prysm-pulse.git
synced 2025-01-19 16:20:53 +00:00
292 lines
11 KiB
Go
292 lines
11 KiB
Go
// Package validators contains libraries to shuffle validators
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// and retrieve active validator indices from a given slot
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// or an attestation. It also provides helper functions to locate
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// validator based on pubic key.
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package validators
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import (
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"encoding/binary"
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"fmt"
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"github.com/prysmaticlabs/prysm/beacon-chain/core/helpers"
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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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)
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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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// 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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// participation_bitfield: bytes) -> List[int]:
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// """
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// Returns the participant indices at for the ``attestation_data`` and ``participation_bitfield``.
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// """
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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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// 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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// assert len(participation_bitfield) == ceil_div8(len(shard_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 = (aggregation_bitfield[i // 8] >> (7 - (i % 8))) % 2
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// if aggregation_bit == 1:
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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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participationBitfield []byte) ([]uint64, error) {
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// Find the relevant committee.
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crosslinkCommittees, err := CrosslinkCommitteesAtSlot(state, attestationData.Slot)
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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 len(participationBitfield) != mathutil.CeilDiv8(len(committee)) {
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return nil, fmt.Errorf(
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"wanted participants bitfield length %d, got: %d",
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mathutil.CeilDiv8(len(committee)),
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len(participationBitfield))
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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(participationBitfield, 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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// CurrCommitteesCountPerSlot returns the number of crosslink committees per slot
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// of the current epoch.
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// Ex: Returns 8 means there's 8 committees assigned to one slot in current epoch.
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//
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// Spec pseudocode definition:
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// def get_current_epoch_committee_count_per_slot(state: BeaconState) -> int:
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// current_active_validators =
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// get_active_validator_indices(validators, state.current_epoch_calculation_slot)
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// return get_committees_per_slot(len(current_active_validators))
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func CurrCommitteesCountPerSlot(state *pb.BeaconState) uint64 {
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currActiveValidatorIndices := ActiveValidatorIndices(
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state.ValidatorRegistry, state.CurrentEpochCalculationSlot)
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return committeeCountPerSlot(uint64(len(currActiveValidatorIndices)))
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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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// def get_crosslink_committees_at_slot(state: BeaconState,
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// slot: SlotNumber) -> List[Tuple[List[ValidatorIndex], ShardNumber]]:
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// """
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// Returns the list of ``(committee, shard)`` tuples for the ``slot``.
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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 = current_epoch - 1 if current_epoch > GENESIS_EPOCH else current_epoch
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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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// committees_per_epoch = get_previous_epoch_committee_count(state)
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// seed = state.previous_epoch_seed
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// shuffling_epoch = state.previous_calculation_epoch
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// shuffling_start_shard = state.previous_epoch_start_shard
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// else:
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// committees_per_epoch = get_current_epoch_committee_count(state)
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// seed = state.current_epoch_seed
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// shuffling_epoch = state.current_calculation_epoch
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// shuffling_start_shard = state.current_epoch_start_shard
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//
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// shuffling = get_shuffling(
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// seed,
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// state.validator_registry,
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// shuffling_epoch,
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// )
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// offset = slot % EPOCH_LENGTH
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// committees_per_slot = committees_per_epoch // EPOCH_LENGTH
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// slot_start_shard = (shuffling_start_shard + committees_per_slot * offset) % SHARD_COUNT
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//
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// return [
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// (
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// shuffling[committees_per_slot * offset + i],
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// (slot_start_shard + i) % SHARD_COUNT,
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// )
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// for i in range(committees_per_slot)
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// ]
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func CrosslinkCommitteesAtSlot(state *pb.BeaconState, slot uint64) ([]*CrosslinkCommittee, error) {
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var countPerSlot uint64
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var startShard uint64
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var shuffledIndices [][]uint64
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var err error
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wantedEpoch := helpers.SlotToEpoch(slot)
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currentEpoch := helpers.CurrentEpoch(state)
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prevEpoch := helpers.PrevEpoch(state)
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nextEpoch := helpers.NextEpoch(state)
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if wantedEpoch < prevEpoch || wantedEpoch >= nextEpoch {
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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,
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prevEpoch,
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currentEpoch,
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)
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}
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offSet := slot % config.EpochLength
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if wantedEpoch < currentEpoch {
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countPerSlot = prevCommitteesCountPerSlot(state)
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shuffledIndices, err = Shuffling(
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bytesutil.ToBytes32(state.PreviousEpochSeedHash32),
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state.ValidatorRegistry,
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state.PreviousEpochCalculationSlot)
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if err != nil {
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return nil, fmt.Errorf("could not shuffle prev epoch validators: %v", err)
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}
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startShard = (state.PreviousEpochStartShard + countPerSlot*offSet) %
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config.ShardCount
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} else {
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countPerSlot = CurrCommitteesCountPerSlot(state)
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shuffledIndices, err = Shuffling(
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bytesutil.ToBytes32(state.CurrentEpochSeedHash32),
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state.ValidatorRegistry,
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state.CurrentEpochCalculationSlot)
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if err != nil {
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return nil, fmt.Errorf("could not shuffle current epoch validators: %v", err)
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}
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startShard = (state.CurrentEpochCalculationSlot + countPerSlot*offSet) %
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config.ShardCount
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}
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var crosslinkCommittees []*CrosslinkCommittee
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for i := uint64(0); i < countPerSlot; i++ {
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crosslinkCommittees = append(crosslinkCommittees, &CrosslinkCommittee{
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Committee: shuffledIndices[countPerSlot*offSet+i],
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Shard: (startShard + i) % config.ShardCount,
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})
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}
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return crosslinkCommittees, nil
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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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// slot: int) -> List[List[int]]
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// """
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// Shuffles ``validators`` into crosslink committees seeded by ``seed`` and ``slot``.
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// Returns a list of ``EPOCH_LENGTH * committees_per_slot`` 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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// # Normalizes slot to start of epoch boundary
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// slot -= slot % EPOCH_LENGTH
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//
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// active_validator_indices = get_active_validator_indices(validators, slot)
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//
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// committees_per_slot = get_committee_count_per_slot(len(active_validator_indices))
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//
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// # Shuffle
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// seed = xor(seed, int_to_bytes32(slot))
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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 epoch_length * committees_per_slot pieces
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// return split(shuffled_active_validator_indices, committees_per_slot * EPOCH_LENGTH)
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func Shuffling(
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seed [32]byte,
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validators []*pb.ValidatorRecord,
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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 % config.EpochLength
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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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committeesPerSlot := committeeCountPerSlot(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.BigEndian.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, committeesPerSlot*config.EpochLength), nil
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}
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// committeeCountPerSlot returns the number of crosslink committees of one slot.
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//
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// Spec pseudocode definition:
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// def get_committee_count_per_slot(active_validator_count: int) -> int:
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// return max(
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// 1,
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// min(
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// SHARD_COUNT // EPOCH_LENGTH,
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// active_validator_count // EPOCH_LENGTH // TARGET_COMMITTEE_SIZE,
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// )
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// )
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func committeeCountPerSlot(activeValidatorCount uint64) uint64 {
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var minCommitteePerSlot = uint64(1)
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var maxCommitteePerSlot = config.ShardCount / config.EpochLength
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var currCommitteePerSlot = activeValidatorCount / config.EpochLength / config.TargetCommitteeSize
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if currCommitteePerSlot > maxCommitteePerSlot {
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return maxCommitteePerSlot
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}
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if currCommitteePerSlot < 1 {
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return minCommitteePerSlot
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}
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return currCommitteePerSlot
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}
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// prevCommitteesCountPerSlot returns the number of committees per slot
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// of the previous epoch.
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// Ex: Returns 16 means there's 16 committees assigned to one slot in previous epoch.
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//
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// Spec pseudocode definition:
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// def get_previous_epoch_committee_count_per_slot(state: BeaconState) -> int:
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// previous_active_validators =
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// get_active_validator_indices(validators, state.previous_epoch_calculation_slot)
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// return get_committees_per_slot(len(previous_active_validators))
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func prevCommitteesCountPerSlot(state *pb.BeaconState) uint64 {
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prevActiveValidatorIndices := ActiveValidatorIndices(
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state.ValidatorRegistry, state.PreviousEpochCalculationSlot)
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return committeeCountPerSlot(uint64(len(prevActiveValidatorIndices)))
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}
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