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Merge pull request #14733 from karalabe/metro-eip100

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consensus/ethash, core: implement Metropolis EIP 100
This commit is contained in:
Péter Szilágyi 2017-07-17 12:43:13 +03:00 committed by GitHub
commit c65f10a17b
2 changed files with 70 additions and 12 deletions
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81
consensus/ethash/consensus.go
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@ -287,8 +287,10 @@ func (ethash *Ethash) verifyHeader(chain consensus.ChainReader, header, parent *
// given the parent block's time and difficulty.
// TODO (karalabe): Move the chain maker into this package and make this private!
func CalcDifficulty(config *params.ChainConfig, time uint64, parent *types.Header) *big.Int {
next := new(big.Int).Add(parent.Number, common.Big1)
next := new(big.Int).Add(parent.Number, big1)
switch {
case config.IsMetropolis(next):
return calcDifficultyMetropolis(time, parent)
case config.IsHomestead(next):
return calcDifficultyHomestead(time, parent)
default:
@ -299,10 +301,65 @@ func CalcDifficulty(config *params.ChainConfig, time uint64, parent *types.Heade
// Some weird constants to avoid constant memory allocs for them.
var (
expDiffPeriod = big.NewInt(100000)
big1 = big.NewInt(1)
big2 = big.NewInt(2)
big9 = big.NewInt(9)
big10 = big.NewInt(10)
bigMinus99 = big.NewInt(-99)
)
// calcDifficultyMetropolis is the difficulty adjustment algorithm. It returns
// the difficulty that a new block should have when created at time given the
// parent block's time and difficulty. The calculation uses the Metropolis rules.
func calcDifficultyMetropolis(time uint64, parent *types.Header) *big.Int {
// https://github.com/ethereum/EIPs/issues/100.
// algorithm:
// diff = (parent_diff +
// (parent_diff / 2048 * max((2 if len(parent.uncles) else 1) - ((timestamp - parent.timestamp) // 9), -99))
// ) + 2^(periodCount - 2)
bigTime := new(big.Int).SetUint64(time)
bigParentTime := new(big.Int).Set(parent.Time)
// holds intermediate values to make the algo easier to read & audit
x := new(big.Int)
y := new(big.Int)
// (2 if len(parent_uncles) else 1) - (block_timestamp - parent_timestamp) // 9
x.Sub(bigTime, bigParentTime)
x.Div(x, big9)
if parent.UncleHash == types.EmptyUncleHash {
x.Sub(big1, x)
} else {
x.Sub(big2, x)
}
// max((2 if len(parent_uncles) else 1) - (block_timestamp - parent_timestamp) // 9, -99)
if x.Cmp(bigMinus99) < 0 {
x.Set(bigMinus99)
}
// (parent_diff + parent_diff // 2048 * max(1 - (block_timestamp - parent_timestamp) // 10, -99))
y.Div(parent.Difficulty, params.DifficultyBoundDivisor)
x.Mul(y, x)
x.Add(parent.Difficulty, x)
// minimum difficulty can ever be (before exponential factor)
if x.Cmp(params.MinimumDifficulty) < 0 {
x.Set(params.MinimumDifficulty)
}
// for the exponential factor
periodCount := new(big.Int).Add(parent.Number, big1)
periodCount.Div(periodCount, expDiffPeriod)
// the exponential factor, commonly referred to as "the bomb"
// diff = diff + 2^(periodCount - 2)
if periodCount.Cmp(big1) > 0 {
y.Sub(periodCount, big2)
y.Exp(big2, y, nil)
x.Add(x, y)
}
return x
}
// calcDifficultyHomestead is the difficulty adjustment algorithm. It returns
// the difficulty that a new block should have when created at time given the
// parent block's time and difficulty. The calculation uses the Homestead rules.
@ -320,12 +377,12 @@ func calcDifficultyHomestead(time uint64, parent *types.Header) *big.Int {
x := new(big.Int)
y := new(big.Int)
// 1 - (block_timestamp -parent_timestamp) // 10
// 1 - (block_timestamp - parent_timestamp) // 10
x.Sub(bigTime, bigParentTime)
x.Div(x, big10)
x.Sub(common.Big1, x)
x.Sub(big1, x)
// max(1 - (block_timestamp - parent_timestamp) // 10, -99)))
// max(1 - (block_timestamp - parent_timestamp) // 10, -99)
if x.Cmp(bigMinus99) < 0 {
x.Set(bigMinus99)
}
@ -339,14 +396,14 @@ func calcDifficultyHomestead(time uint64, parent *types.Header) *big.Int {
x.Set(params.MinimumDifficulty)
}
// for the exponential factor
periodCount := new(big.Int).Add(parent.Number, common.Big1)
periodCount := new(big.Int).Add(parent.Number, big1)
periodCount.Div(periodCount, expDiffPeriod)
// the exponential factor, commonly referred to as "the bomb"
// diff = diff + 2^(periodCount - 2)
if periodCount.Cmp(common.Big1) > 0 {
y.Sub(periodCount, common.Big2)
y.Exp(common.Big2, y, nil)
if periodCount.Cmp(big1) > 0 {
y.Sub(periodCount, big2)
y.Exp(big2, y, nil)
x.Add(x, y)
}
return x
@ -373,12 +430,12 @@ func calcDifficultyFrontier(time uint64, parent *types.Header) *big.Int {
diff.Set(params.MinimumDifficulty)
}
periodCount := new(big.Int).Add(parent.Number, common.Big1)
periodCount := new(big.Int).Add(parent.Number, big1)
periodCount.Div(periodCount, expDiffPeriod)
if periodCount.Cmp(common.Big1) > 0 {
if periodCount.Cmp(big1) > 0 {
// diff = diff + 2^(periodCount - 2)
expDiff := periodCount.Sub(periodCount, common.Big2)
expDiff.Exp(common.Big2, expDiff, nil)
expDiff := periodCount.Sub(periodCount, big2)
expDiff.Exp(big2, expDiff, nil)
diff.Add(diff, expDiff)
diff = math.BigMax(diff, params.MinimumDifficulty)
}

1
core/chain_makers.go
View File

@ -218,6 +218,7 @@ func makeHeader(config *params.ChainConfig, parent *types.Block, state *state.St
Number: parent.Number(),
Time: new(big.Int).Sub(time, big.NewInt(10)),
Difficulty: parent.Difficulty(),
UncleHash: parent.UncleHash(),
}),
GasLimit: CalcGasLimit(parent),
GasUsed: new(big.Int),