consensus/ethash: implement Metropolis EIP 100

This commit is contained in:
Jeffrey Wilcke 2017-06-30 16:39:18 +03:00 committed by Péter Szilágyi
parent a0aa071ca6
commit c4d28aee9b
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1 changed files with 48 additions and 0 deletions

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@ -289,6 +289,8 @@ func (ethash *Ethash) verifyHeader(chain consensus.ChainReader, header, parent *
func CalcDifficulty(config *params.ChainConfig, time uint64, parent *types.Header) *big.Int { 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, common.Big1)
switch { switch {
case config.IsMetropolis(next):
return calcDifficultyMetropolis(time, parent)
case config.IsHomestead(next): case config.IsHomestead(next):
return calcDifficultyHomestead(time, parent) return calcDifficultyHomestead(time, parent)
default: default:
@ -299,10 +301,56 @@ func CalcDifficulty(config *params.ChainConfig, time uint64, parent *types.Heade
// Some weird constants to avoid constant memory allocs for them. // Some weird constants to avoid constant memory allocs for them.
var ( var (
expDiffPeriod = big.NewInt(100000) expDiffPeriod = big.NewInt(100000)
big9 = big.NewInt(9)
big10 = big.NewInt(10) big10 = big.NewInt(10)
bigMinus99 = big.NewInt(-99) bigMinus99 = big.NewInt(-99)
) )
func calcDifficultyMetropolis(time uint64, parent *types.Header) *big.Int {
bigTime := new(big.Int).SetUint64(time)
bigParentTime := new(big.Int).Set(parent.Time)
// adj_factor = max((2 if len(parent.uncles) else 1) - ((timestamp - parent.timestamp) // 9), -99)
var x *big.Int
if parent.UncleHash == types.EmptyUncleHash {
x = big.NewInt(1)
} else {
x = big.NewInt(2)
}
z := new(big.Int).Sub(bigTime, bigParentTime)
z.Div(z, big9)
x.Sub(x, z)
// max(1 - (block_timestamp - parent_timestamp) // 10, -99)))
if x.Cmp(bigMinus99) < 0 {
x.Set(bigMinus99)
}
// (parent_diff + parent_diff // 2048 * max(1 - (block_timestamp - parent_timestamp) // 10, -99))
y := new(big.Int).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, common.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)
x.Add(x, y)
}
return x
}
// calcDifficultyHomestead is the difficulty adjustment algorithm. It returns // calcDifficultyHomestead is the difficulty adjustment algorithm. It returns
// the difficulty that a new block should have when created at time given the // 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. // parent block's time and difficulty. The calculation uses the Homestead rules.