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80 lines
1.8 KiB
80 lines
1.8 KiB
package effective
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import (
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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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"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 stake(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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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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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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return stakes[(l/2)-1].Dec.Add(stakes[(l/2)+1].Dec).Quo(two)
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default:
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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) 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 := int64(len(shortHand[staker].SpreadAmong))
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spread := numeric.NewDecFromBigInt(shortHand[staker].Stake).QuoInt64(slotsCount)
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var i int64
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for ; i < slotsCount; i++ {
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eposedSlots = append(eposedSlots, SlotPurchase{staker, spread})
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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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median := median(eposedSlots)
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for i := range eposedSlots {
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eposedSlots[i].Dec = stake(median, eposedSlots[i].Dec)
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}
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return eposedSlots
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}
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