prysm-pulse/beacon-chain/core/balances/rewards_penalties.go
Nishant Das c48f9c96e0
Allow Simulated Backend to Advance Chain (#1445)
* initialize beacon state separately

* extracting out testcase into another func

* creating function for simulated objects

* creating simulated object struct

* final clean up

* documentation

* lint

* adding chain advancer

* review comments

* replacing lib

* adding initialization for chain and new vars in struct

* added func

* fixing tests and all other bugs

* fixing tests

* docs

* adding a new nil block function

* adding test

* remove check for nil blocks

* godoc

* fixing merge conflicts, tests

* fix test
2019-02-06 10:18:55 +08:00

435 lines
16 KiB
Go

// Package balances contains libraries to calculate reward and
// penalty quotients. It computes new validator balances
// for justifications, crosslinks and attestation inclusions. It
// also computes penalties for the inactive validators.
package balances
import (
"errors"
"fmt"
"github.com/prysmaticlabs/prysm/beacon-chain/core/epoch"
"github.com/prysmaticlabs/prysm/beacon-chain/core/helpers"
"github.com/prysmaticlabs/prysm/beacon-chain/core/validators"
pb "github.com/prysmaticlabs/prysm/proto/beacon/p2p/v1"
"github.com/prysmaticlabs/prysm/shared/mathutil"
"github.com/prysmaticlabs/prysm/shared/params"
"github.com/prysmaticlabs/prysm/shared/sliceutil"
)
var config = params.BeaconConfig()
// ExpectedFFGSource applies rewards or penalties
// for an expected FFG source. It uses total justified
// attesting balances, total validator balances and base
// reward quotient to calculate the reward amount.
// Validators who voted for previous justified hash
// will get a reward, everyone else will get a penalty.
//
// Spec pseudocode definition:
// Any validator index in previous_epoch_justified_attester_indices
// gains base_reward(state, index) * previous_epoch_justified_attesting_balance // total_balance.
// Any active validator v not in previous_epoch_justified_attester_indices
// loses base_reward(state, index).
func ExpectedFFGSource(
state *pb.BeaconState,
justifiedAttesterIndices []uint64,
justifiedAttestingBalance uint64,
totalBalance uint64) *pb.BeaconState {
baseRewardQuotient := baseRewardQuotient(totalBalance)
for _, index := range justifiedAttesterIndices {
state.ValidatorBalances[index] +=
baseReward(state, index, baseRewardQuotient) *
justifiedAttestingBalance /
totalBalance
}
activeValidatorIndices := helpers.ActiveValidatorIndices(state.ValidatorRegistry, state.Slot)
didNotAttestIndices := sliceutil.Not(justifiedAttesterIndices, activeValidatorIndices)
for _, index := range didNotAttestIndices {
state.ValidatorBalances[index] -=
baseReward(state, index, baseRewardQuotient)
}
return state
}
// ExpectedFFGTarget applies rewards or penalties
// for an expected FFG target. It uses total boundary
// attesting balances, total validator balances and base
// reward quotient to calculate the reward amount.
// Validators who voted for epoch boundary block
// will get a reward, everyone else will get a penalty.
//
// Spec pseudocode definition:
// Any validator index in previous_epoch_boundary_attester_indices gains
// base_reward(state, index) * previous_epoch_boundary_attesting_balance // total_balance.
// Any active validator index not in previous_epoch_boundary_attester_indices loses
// base_reward(state, index).
func ExpectedFFGTarget(
state *pb.BeaconState,
boundaryAttesterIndices []uint64,
boundaryAttestingBalance uint64,
totalBalance uint64) *pb.BeaconState {
baseRewardQuotient := baseRewardQuotient(totalBalance)
for _, index := range boundaryAttesterIndices {
state.ValidatorBalances[index] +=
baseReward(state, index, baseRewardQuotient) *
boundaryAttestingBalance /
totalBalance
}
activeValidatorIndices := helpers.ActiveValidatorIndices(state.ValidatorRegistry, state.Slot)
didNotAttestIndices := sliceutil.Not(boundaryAttesterIndices, activeValidatorIndices)
for _, index := range didNotAttestIndices {
state.ValidatorBalances[index] -=
baseReward(state, index, baseRewardQuotient)
}
return state
}
// ExpectedBeaconChainHead applies rewards or penalties
// for an expected beacon chain head. It uses total head
// attesting balances, total validator balances and base
// reward quotient to calculate the reward amount.
// Validators who voted for the canonical head block
// will get a reward, everyone else will get a penalty.
//
// Spec pseudocode definition:
// Any validator index in previous_epoch_head_attester_indices gains
// base_reward(state, index) * previous_epoch_head_attesting_balance // total_balance).
// Any active validator index not in previous_epoch_head_attester_indices loses
// base_reward(state, index).
func ExpectedBeaconChainHead(
state *pb.BeaconState,
headAttesterIndices []uint64,
headAttestingBalance uint64,
totalBalance uint64) *pb.BeaconState {
baseRewardQuotient := baseRewardQuotient(totalBalance)
for _, index := range headAttesterIndices {
state.ValidatorBalances[index] +=
baseReward(state, index, baseRewardQuotient) *
headAttestingBalance /
totalBalance
}
activeValidatorIndices := helpers.ActiveValidatorIndices(state.ValidatorRegistry, state.Slot)
didNotAttestIndices := sliceutil.Not(headAttesterIndices, activeValidatorIndices)
for _, index := range didNotAttestIndices {
state.ValidatorBalances[index] -=
baseReward(state, index, baseRewardQuotient)
}
return state
}
// InclusionDistance applies rewards based on
// inclusion distance. It uses calculated inclusion distance
// and base reward quotient to calculate the reward amount.
//
// Spec pseudocode definition:
// Any validator index in previous_epoch_attester_indices gains
// base_reward(state, index) * MIN_ATTESTATION_INCLUSION_DELAY //
// inclusion_distance(state, index)
func InclusionDistance(
state *pb.BeaconState,
attesterIndices []uint64,
totalBalance uint64) (*pb.BeaconState, error) {
baseRewardQuotient := baseRewardQuotient(totalBalance)
for _, index := range attesterIndices {
inclusionDistance, err := epoch.InclusionDistance(state, index)
if err != nil {
return nil, fmt.Errorf("could not get inclusion distance: %v", err)
}
if inclusionDistance == 0 {
return nil, errors.New("could not process inclusion distance: 0")
}
state.ValidatorBalances[index] +=
baseReward(state, index, baseRewardQuotient) *
config.MinAttestationInclusionDelay /
inclusionDistance
}
return state, nil
}
// InactivityFFGSource applies penalties to inactive
// validators that missed to vote FFG source over an
// extended of time. (epochs_since_finality > 4)
//
// Spec pseudocode definition:
// Any active validator index not in previous_epoch_justified_attester_indices,
// loses inactivity_penalty(state, index, epochs_since_finality)
func InactivityFFGSource(
state *pb.BeaconState,
justifiedAttesterIndices []uint64,
totalBalance uint64,
epochsSinceFinality uint64) *pb.BeaconState {
baseRewardQuotient := baseRewardQuotient(totalBalance)
activeValidatorIndices := helpers.ActiveValidatorIndices(state.ValidatorRegistry, state.Slot)
didNotAttestIndices := sliceutil.Not(justifiedAttesterIndices, activeValidatorIndices)
for _, index := range didNotAttestIndices {
state.ValidatorBalances[index] -=
inactivityPenalty(state, index, baseRewardQuotient, epochsSinceFinality)
}
return state
}
// InactivityFFGTarget applies penalties to inactive
// validators that missed to vote FFG target over an
// extended of time. (epochs_since_finality > 4)
//
// Spec pseudocode definition:
// Any active validator index not in previous_epoch_boundary_attester_indices,
// loses inactivity_penalty(state, index, epochs_since_finality)
func InactivityFFGTarget(
state *pb.BeaconState,
boundaryAttesterIndices []uint64,
totalBalance uint64,
epochsSinceFinality uint64) *pb.BeaconState {
baseRewardQuotient := baseRewardQuotient(totalBalance)
activeValidatorIndices := helpers.ActiveValidatorIndices(state.ValidatorRegistry, state.Slot)
didNotAttestIndices := sliceutil.Not(boundaryAttesterIndices, activeValidatorIndices)
for _, index := range didNotAttestIndices {
state.ValidatorBalances[index] -=
inactivityPenalty(state, index, baseRewardQuotient, epochsSinceFinality)
}
return state
}
// InactivityChainHead applies penalties to inactive validators
// that missed to vote on canonical head over an extended of time.
// (epochs_since_finality > 4)
//
// Spec pseudocode definition:
// Any active validator index not in previous_epoch_head_attester_indices,
// loses base_reward(state, index)
func InactivityChainHead(
state *pb.BeaconState,
headAttesterIndices []uint64,
totalBalance uint64) *pb.BeaconState {
baseRewardQuotient := baseRewardQuotient(totalBalance)
activeValidatorIndices := helpers.ActiveValidatorIndices(state.ValidatorRegistry, state.Slot)
didNotAttestIndices := sliceutil.Not(headAttesterIndices, activeValidatorIndices)
for _, index := range didNotAttestIndices {
state.ValidatorBalances[index] -=
baseReward(state, index, baseRewardQuotient)
}
return state
}
// InactivityExitedPenalties applies additional (2x) penalties
// to inactive validators with status EXITED_WITH_PENALTY.
//
// Spec pseudocode definition:
// Any active_validator index with validator.penalized_epoch <= current_epoch,
// loses 2 * inactivity_penalty(state, index, epochs_since_finality) +
// base_reward(state, index).
func InactivityExitedPenalties(
state *pb.BeaconState,
totalBalance uint64,
epochsSinceFinality uint64) *pb.BeaconState {
baseRewardQuotient := baseRewardQuotient(totalBalance)
activeValidatorIndices := helpers.ActiveValidatorIndices(state.ValidatorRegistry, state.Slot)
for _, index := range activeValidatorIndices {
if state.ValidatorRegistry[index].PenalizedEpoch <= helpers.CurrentEpoch(state) {
state.ValidatorBalances[index] -=
2*inactivityPenalty(state, index, baseRewardQuotient, epochsSinceFinality) +
baseReward(state, index, baseRewardQuotient)
}
}
return state
}
// InactivityInclusionDistance applies penalties in relation with
// inclusion delay to inactive validators.
//
// Spec pseudocode definition:
// Any validator index in previous_epoch_attester_indices loses
// base_reward(state, index) - base_reward(state, index) *
// MIN_ATTESTATION_INCLUSION_DELAY // inclusion_distance(state, index)
func InactivityInclusionDistance(
state *pb.BeaconState,
attesterIndices []uint64,
totalBalance uint64) (*pb.BeaconState, error) {
baseRewardQuotient := baseRewardQuotient(totalBalance)
for _, index := range attesterIndices {
inclusionDistance, err := epoch.InclusionDistance(state, index)
if err != nil {
return nil, fmt.Errorf("could not get inclusion distance: %v", err)
}
baseReward := baseReward(state, index, baseRewardQuotient)
state.ValidatorBalances[index] -= baseReward -
baseReward*config.MinAttestationInclusionDelay/
inclusionDistance
}
return state, nil
}
// AttestationInclusion awards the the beacon
// proposers who included previous epoch attestations.
//
// Spec pseudocode definition:
// For each index in previous_epoch_attester_indices,
// we determine the proposer proposer_index =
// get_beacon_proposer_index(state, inclusion_slot(state, index))
// and set state.validator_balances[proposer_index] +=
// base_reward(state, index) // INCLUDER_REWARD_QUOTIENT
func AttestationInclusion(
state *pb.BeaconState,
totalBalance uint64,
prevEpochAttesterIndices []uint64) (*pb.BeaconState, error) {
baseRewardQuotient := baseRewardQuotient(totalBalance)
for _, index := range prevEpochAttesterIndices {
slot, err := epoch.InclusionSlot(state, index)
if err != nil {
return nil, fmt.Errorf("could not get inclusion slot: %v", err)
}
proposerIndex, err := validators.BeaconProposerIdx(state, slot)
if err != nil {
return nil, fmt.Errorf("could not get propoer index: %v", err)
}
state.ValidatorBalances[proposerIndex] +=
baseReward(state, proposerIndex, baseRewardQuotient) /
config.IncluderRewardQuotient
}
return state, nil
}
// Crosslinks awards or penalizes attesters
// for attesting shard cross links.
//
// Spec pseudocode definition:
// For slot in range(get_epoch_start_slot(previous_epoch), get_epoch_start_slot(current_epoch)),
// let crosslink_committees_at_slot = get_crosslink_committees_at_slot(slot).
// For every (crosslink_committee, shard) in crosslink_committee_at_slot, compute:
//
// Let shard_block_root be state.latest_crosslinks[shard].shard_block_root
// Let attesting_validator_indices(shard_committee, shard_block_root)
// be the union of the validator index sets given by [get_attestation_participants(
// state, a.data, a.participation_bitfield) for a in current_epoch_attestations +
// previous_epoch_attestations if a.shard == shard and a.shard_block_root == shard_block_root].
// Let winning_root(shard_committee)
// be equal to the value of shard_block_root such that sum([get_effective_balance(state, i)
// for i in attesting_validator_indices(shard_committee, shard_block_root)])
// is maximized (ties broken by favoring lower shard_block_root values).
// Let attesting_validators(shard_committee)
// be equal to attesting_validator_indices(
// shard_committee, winning_root(shard_committee)) for convenience.
// Let total_attesting_balance(shard_committee) =
// sum([get_effective_balance(state, i) for i in attesting_validators(shard_committee)]).
// Let total_balance(shard_committee) =
// sum([get_effective_balance(state, i) for i in shard_committee]).
func Crosslinks(
state *pb.BeaconState,
thisEpochAttestations []*pb.PendingAttestationRecord,
prevEpochAttestations []*pb.PendingAttestationRecord) (*pb.BeaconState, error) {
prevEpoch := helpers.PrevEpoch(state)
currentEpoch := helpers.CurrentEpoch(state)
startSlot := helpers.StartSlot(prevEpoch)
endSlot := helpers.StartSlot(currentEpoch)
for i := startSlot; i < endSlot; i++ {
crosslinkCommittees, err := helpers.CrosslinkCommitteesAtSlot(state, i, false)
if err != nil {
return nil, fmt.Errorf("could not get shard committees for slot %d: %v", i, err)
}
for _, crosslinkCommittee := range crosslinkCommittees {
shard := crosslinkCommittee.Shard
committee := crosslinkCommittee.Committee
totalAttestingBalance, err :=
epoch.TotalAttestingBalance(state, shard, thisEpochAttestations, prevEpochAttestations)
if err != nil {
return nil,
fmt.Errorf("could not get attesting balance for shard committee %d: %v", shard, err)
}
totalBalance := epoch.TotalBalance(state, committee)
baseRewardQuotient := baseRewardQuotient(totalBalance)
attestingIndices, err := epoch.AttestingValidators(
state,
shard,
thisEpochAttestations,
prevEpochAttestations)
if err != nil {
return nil,
fmt.Errorf("could not get attesting indices for shard committee %d: %v", shard, err)
}
for _, index := range committee {
baseReward := baseReward(state, index, baseRewardQuotient)
if sliceutil.IsIn(index, attestingIndices) {
state.ValidatorBalances[index] +=
baseReward * totalAttestingBalance / totalBalance
} else {
state.ValidatorBalances[index] -=
baseReward * totalAttestingBalance / totalBalance
}
}
}
}
return state, nil
}
// baseRewardQuotient takes the total balance and calculates for
// the quotient of the base reward.
//
// Spec pseudocode definition:
// base_reward_quotient =
// integer_squareroot(total_balance) // BASE_REWARD_QUOTIENT
func baseRewardQuotient(totalBalance uint64) uint64 {
return mathutil.IntegerSquareRoot(totalBalance) / params.BeaconConfig().BaseRewardQuotient
}
// baseReward takes state and validator index to calculate for
// individual validator's base reward.
//
// Spec pseudocode definition:
// base_reward(state, index) =
// get_effective_balance(state, index) // base_reward_quotient // 5
func baseReward(
state *pb.BeaconState,
validatorIndex uint64,
baseRewardQuotient uint64) uint64 {
validatorBalance := validators.EffectiveBalance(state, validatorIndex)
return validatorBalance / baseRewardQuotient / 5
}
// inactivityPenalty takes state and validator index to calculate for
// individual validator's penalty for being offline.
//
// Spec pseudocode definition:
// inactivity_penalty(state, index, epochs_since_finality) =
// base_reward(state, index) + get_effective_balance(state, index)
// * epochs_since_finality // INACTIVITY_PENALTY_QUOTIENT // 2
func inactivityPenalty(
state *pb.BeaconState,
validatorIndex uint64,
baseRewardQuotient uint64,
epochsSinceFinality uint64) uint64 {
baseReward := baseReward(state, validatorIndex, baseRewardQuotient)
validatorBalance := validators.EffectiveBalance(state, validatorIndex)
return baseReward + validatorBalance*epochsSinceFinality/config.InactivityPenaltyQuotient/2
}