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125 lines
2.9 KiB
125 lines
2.9 KiB
package effective
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import (
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"encoding/json"
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"math/big"
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"sort"
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"github.com/ethereum/go-ethereum/common"
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common2 "github.com/harmony-one/harmony/internal/common"
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"github.com/harmony-one/harmony/internal/utils"
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"github.com/harmony-one/harmony/numeric"
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"github.com/harmony-one/harmony/shard"
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)
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// medium.com/harmony-one/introducing-harmonys-effective-proof-of-stake-epos-2d39b4b8d58
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var (
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two = numeric.NewDecFromBigInt(big.NewInt(2))
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c, _ = numeric.NewDecFromStr("0.15")
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onePlusC = numeric.OneDec().Add(c)
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oneMinusC = numeric.OneDec().Sub(c)
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)
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func effectiveStake(median, actual numeric.Dec) numeric.Dec {
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left := numeric.MinDec(onePlusC.Mul(median), actual)
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right := oneMinusC.Mul(median)
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return numeric.MaxDec(left, right)
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}
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// SlotPurchase ..
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type SlotPurchase struct {
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common.Address `json:"slot-owner"`
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shard.BlsPublicKey `json:"bls-public-key"`
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numeric.Dec `json:"eposed-stake"`
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}
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// SlotOrder ..
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type SlotOrder struct {
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Stake *big.Int
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SpreadAmong []shard.BlsPublicKey
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}
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// Slots ..
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type Slots []SlotPurchase
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// JSON is a plain JSON dump
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func (s Slots) JSON() string {
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type t struct {
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Address string `json:"slot-owner"`
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Key string `json:"bls-public-key"`
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Stake string `json:"actual-stake"`
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}
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type v struct {
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Slots []t `json:"slots"`
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}
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data := v{}
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for i := range s {
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newData := t{
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common2.MustAddressToBech32(s[i].Address),
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s[i].BlsPublicKey.Hex(),
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s[i].Dec.String(),
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}
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data.Slots = append(data.Slots, newData)
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}
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b, _ := json.Marshal(data)
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return string(b)
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}
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func median(stakes []SlotPurchase) numeric.Dec {
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sort.SliceStable(
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stakes,
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func(i, j int) bool { return stakes[i].Dec.LTE(stakes[j].Dec) },
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)
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const isEven = 0
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switch l := len(stakes); l % 2 {
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case isEven:
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left := (l / 2) - 1
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right := (l / 2)
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utils.Logger().Info().Int("left", left).Int("right", right)
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return stakes[left].Dec.Add(stakes[right].Dec).Quo(two)
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default:
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utils.Logger().Info().Int("median index", l/2)
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return stakes[l/2].Dec
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}
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}
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// Apply ..
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func Apply(shortHand map[common.Address]SlotOrder, pull int) Slots {
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eposedSlots := Slots{}
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if len(shortHand) == 0 {
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return eposedSlots
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}
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// Expand
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for staker := range shortHand {
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slotsCount := len(shortHand[staker].SpreadAmong)
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spread := numeric.NewDecFromBigInt(shortHand[staker].Stake).
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QuoInt64(int64(slotsCount))
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for i := 0; i < slotsCount; i++ {
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eposedSlots = append(eposedSlots, SlotPurchase{
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staker,
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shortHand[staker].SpreadAmong[i],
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spread,
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})
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}
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}
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if len(eposedSlots) < len(shortHand) {
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// WARN Should never happen
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}
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sort.SliceStable(
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eposedSlots,
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func(i, j int) bool { return eposedSlots[i].Dec.GT(eposedSlots[j].Dec) },
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)
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if l := len(eposedSlots); l < pull {
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pull = l
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}
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picks := eposedSlots[:pull]
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median := median(picks)
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for i := range picks {
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picks[i].Dec = effectiveStake(median, picks[i].Dec)
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}
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return picks
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}
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