mirror of
https://github.com/ethereum/go-ethereum.git
synced 2026-07-26 06:36:43 +00:00
Rewrite difficulty adjustment algorithm. Based on Digibyte's Digishield V3
This commit is contained in:
Julian Yap
parent
a542816c86
commit
f5f7b50afd
2 changed files with 106 additions and 71 deletions
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@ -24,6 +24,7 @@ import (
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"github.com/ubiq/go-ubiq/common"
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"github.com/ubiq/go-ubiq/core/state"
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"github.com/ubiq/go-ubiq/core/types"
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"github.com/ubiq/go-ubiq/logger"
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"github.com/ubiq/go-ubiq/logger/glog"
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"github.com/ubiq/go-ubiq/params"
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"github.com/ubiq/go-ubiq/pow"
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@ -31,11 +32,41 @@ import (
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)
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var (
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ExpDiffPeriod = big.NewInt(100000)
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big10 = big.NewInt(10)
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bigMinus99 = big.NewInt(-99)
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ExpDiffPeriod = big.NewInt(100000)
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big88 = big.NewInt(88)
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bigMinus99 = big.NewInt(-99)
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nPowAveragingWindow = big.NewInt(21)
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nPowMaxAdjustDown = big.NewInt(16) // 16% adjustment down
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nPowMaxAdjustUp = big.NewInt(8) // 8% adjustment up
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)
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func AveragingWindowTimespan() *big.Int {
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x := new(big.Int)
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return x.Mul(nPowAveragingWindow, big88)
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}
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func MinActualTimespan() *big.Int {
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// (AveragingWindowTimespan() * (100 - nPowMaxAdjustUp )) / 100
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x := new(big.Int)
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y := new(big.Int)
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z := new(big.Int)
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x.Sub(big.NewInt(100), nPowMaxAdjustUp)
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y.Mul(AveragingWindowTimespan(), x)
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z.Div(y, big.NewInt(100))
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return z
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}
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func MaxActualTimespan() *big.Int {
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// (AveragingWindowTimespan() * (100 + nPowMaxAdjustDown)) / 100
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x := new(big.Int)
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y := new(big.Int)
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z := new(big.Int)
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x.Add(big.NewInt(100), nPowMaxAdjustDown)
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y.Mul(AveragingWindowTimespan(), x)
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z.Div(y, big.NewInt(100))
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return z
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}
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// BlockValidator is responsible for validating block headers, uncles and
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// processed state.
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//
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@ -310,87 +341,100 @@ func ValidateHeaderHeaderChain(config *params.ChainConfig, pow pow.PoW, header *
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// CalcDifficulty is the difficulty adjustment algorithm. It returns
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// the difficulty that a new block should have when created at time
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// given the parent block's time and difficulty.
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// Rewritten to be based on Digibyte's Digishield v3 retargeting
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func CalcDifficulty(config *params.ChainConfig, time, parentTime uint64, parentNumber, parentDiff *big.Int, bc *BlockChain) *big.Int {
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// https://github.com/ethereum/EIPs/blob/master/EIPS/eip-2.mediawiki
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// algorithm:
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// diff = (parent_diff +
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// (parent_diff / 2048 * max(1 - (block_timestamp - parent_timestamp) // 10, -99))
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// ) + 2^(periodCount - 2)
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bigTime := new(big.Int).SetUint64(time)
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bigParentTime := new(big.Int).SetUint64(parentTime)
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// holds intermediate values to make the algo easier to read & audit
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x := new(big.Int)
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y := new(big.Int)
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nFirstBlock := new(big.Int)
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nFirstBlock.Sub(parentNumber, nPowAveragingWindow)
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// 1 - (block_timestamp -parent_timestamp) // 10
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x.Sub(bigTime, bigParentTime)
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x.Div(x, big10)
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x.Sub(common.Big1, x)
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glog.V(logger.Debug).Infof("CalcDifficulty parentNumber: %v parentDiff: %v\n", parentNumber, parentDiff)
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// max(1 - (block_timestamp - parent_timestamp) // 10, -99)))
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if x.Cmp(bigMinus99) < 0 {
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x.Set(bigMinus99)
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// Check we have enough blocks
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if parentNumber.Cmp(nPowAveragingWindow) < 1 {
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glog.V(logger.Debug).Infof("CalcDifficulty: parentNumber(%+x) < nPowAveragingWindow(%+x)\n", parentNumber, nPowAveragingWindow)
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x.Set(parentDiff)
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return x
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}
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// (parent_diff + parent_diff // 2048 * max(1 - (block_timestamp - parent_timestamp) // 10, -99))
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y.Div(parentDiff, params.DifficultyBoundDivisor)
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x.Mul(y, x)
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x.Add(parentDiff, x)
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// Limit adjustment step
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// Use medians to prevent time-warp attacks
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// nActualTimespan := nLastBlockTime - nFirstBlockTime
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nLastBlockTime := bc.CalcPastMedianTime(parentNumber.Uint64())
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nFirstBlockTime := bc.CalcPastMedianTime(nFirstBlock.Uint64())
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nActualTimespan := new(big.Int)
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nActualTimespan.Sub(nLastBlockTime, nFirstBlockTime)
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glog.V(logger.Debug).Infof("CalcDifficulty nActualTimespan = %v before dampening\n", nActualTimespan)
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// nActualTimespan = AveragingWindowTimespan() + (nActualTimespan-AveragingWindowTimespan())/4
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y := new(big.Int)
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y.Sub(nActualTimespan, AveragingWindowTimespan())
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y.Div(y, big.NewInt(4))
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nActualTimespan.Add(y, AveragingWindowTimespan())
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glog.V(logger.Debug).Infof("CalcDifficulty nActualTimespan = %v before bounds\n", nActualTimespan)
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if nActualTimespan.Cmp(MinActualTimespan()) < 0 {
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nActualTimespan.Set(MinActualTimespan())
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glog.V(logger.Debug).Infoln("CalcDifficulty Minimum Timespan set")
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} else if nActualTimespan.Cmp(MaxActualTimespan()) > 0 {
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nActualTimespan.Set(MaxActualTimespan())
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glog.V(logger.Debug).Infoln("CalcDifficulty Maximum Timespan set")
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}
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glog.V(logger.Debug).Infof("CalcDifficulty nActualTimespan = %v final\n", nActualTimespan)
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// Retarget
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x.Mul(parentDiff, AveragingWindowTimespan())
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glog.V(logger.Debug).Infoln("CalcDifficulty parentDiff * AveragingWindowTimespan:", x)
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x.Div(x, nActualTimespan)
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glog.V(logger.Debug).Infoln("CalcDifficulty x / nActualTimespan:", x)
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// minimum difficulty can ever be (before exponential factor)
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if x.Cmp(params.MinimumDifficulty) < 0 {
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x.Set(params.MinimumDifficulty)
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}
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// for the exponential factor
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periodCount := new(big.Int).Add(parentNumber, common.Big1)
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periodCount.Div(periodCount, ExpDiffPeriod)
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// the exponential factor, commonly referred to as "the bomb"
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// diff = diff + 2^(periodCount - 2)
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if periodCount.Cmp(common.Big1) > 0 {
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y.Sub(periodCount, common.Big2)
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y.Exp(common.Big2, y, nil)
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x.Add(x, y)
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}
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return x
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}
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func CalcDifficultyHeaderChain(config *params.ChainConfig, time, parentTime uint64, parentNumber, parentDiff *big.Int, hc *HeaderChain) *big.Int {
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bigTime := new(big.Int).SetUint64(time)
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bigParentTime := new(big.Int).SetUint64(parentTime)
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// holds intermediate values to make the algo easier to read & audit
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x := new(big.Int)
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y := new(big.Int)
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nFirstBlock := new(big.Int)
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nFirstBlock.Sub(parentNumber, nPowAveragingWindow)
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x.Sub(bigTime, bigParentTime)
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x.Div(x, big10)
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x.Sub(common.Big1, x)
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if x.Cmp(bigMinus99) < 0 {
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x.Set(bigMinus99)
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// Check we have enough blocks
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if parentNumber.Cmp(nPowAveragingWindow) < 1 {
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x.Set(parentDiff)
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return x
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}
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y.Div(parentDiff, params.DifficultyBoundDivisor)
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x.Mul(y, x)
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x.Add(parentDiff, x)
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nLastBlockTime := hc.CalcPastMedianTime(parentNumber.Uint64())
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nFirstBlockTime := hc.CalcPastMedianTime(nFirstBlock.Uint64())
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nActualTimespan := new(big.Int)
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nActualTimespan.Sub(nLastBlockTime, nFirstBlockTime)
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y := new(big.Int)
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y.Sub(nActualTimespan, AveragingWindowTimespan())
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y.Div(y, big.NewInt(4))
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nActualTimespan.Add(y, AveragingWindowTimespan())
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if nActualTimespan.Cmp(MinActualTimespan()) < 0 {
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nActualTimespan.Set(MinActualTimespan())
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} else if nActualTimespan.Cmp(MaxActualTimespan()) > 0 {
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nActualTimespan.Set(MaxActualTimespan())
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}
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// Retarget
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x.Mul(parentDiff, AveragingWindowTimespan())
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x.Div(x, nActualTimespan)
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// minimum difficulty can ever be (before exponential factor)
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if x.Cmp(params.MinimumDifficulty) < 0 {
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x.Set(params.MinimumDifficulty)
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}
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periodCount := new(big.Int).Add(parentNumber, common.Big1)
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periodCount.Div(periodCount, ExpDiffPeriod)
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if periodCount.Cmp(common.Big1) > 0 {
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y.Sub(periodCount, common.Big2)
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y.Exp(common.Big2, y, nil)
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x.Add(x, y)
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}
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return x
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}
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@ -402,7 +446,7 @@ func CalcDifficultyLegacy(config *params.ChainConfig, time, parentTime uint64, p
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y := new(big.Int)
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x.Sub(bigTime, bigParentTime)
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x.Div(x, big10)
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x.Div(x, big88)
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x.Sub(common.Big1, x)
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if x.Cmp(bigMinus99) < 0 {
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@ -417,15 +461,6 @@ func CalcDifficultyLegacy(config *params.ChainConfig, time, parentTime uint64, p
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x.Set(params.MinimumDifficulty)
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}
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periodCount := new(big.Int).Add(parentNumber, common.Big1)
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periodCount.Div(periodCount, ExpDiffPeriod)
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if periodCount.Cmp(common.Big1) > 0 {
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y.Sub(periodCount, common.Big2)
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y.Exp(common.Big2, y, nil)
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x.Add(x, y)
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}
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return x
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}
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@ -359,7 +359,7 @@ func (hc *HeaderChain) GetBlockHashesFromHash(hash common.Hash, max uint64) []co
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func (hc *HeaderChain) GetBlockHeadersFromHash(hash common.Hash, max uint64) []*types.Header {
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// Get the origin header from which to fetch
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header := hc.GetHeader(hash)
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header := hc.GetHeaderByHash(hash)
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if header == nil {
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return nil
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}
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@ -367,10 +367,10 @@ func (hc *HeaderChain) GetBlockHeadersFromHash(hash common.Hash, max uint64) []*
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chain := make([]*types.Header, 0, max)
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for i := uint64(0); i < max; i++ {
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next := header.ParentHash
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if header = hc.GetHeader(next); header == nil {
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if header = hc.GetHeaderByHash(next); header == nil {
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break
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}
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chain = append(chain, hc.GetHeader(next))
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chain = append(chain, hc.GetHeaderByHash(next))
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if header.Number.Cmp(common.Big0) == 0 {
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break
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}
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