interesting
/
go-ethereum
mirror of https://github.com/ethereum/go-ethereum.git
1
0
Fork 0
Code Issues Projects Releases Wiki Activity

consensus, core: EIP 100 polishes, fix chain maker diff 

This PR polishes the EIP 100 difficulty adjustment algorithm
to match the same mechanisms as the Homestead was implemented
to keep the code uniform. It also avoids a few memory allocs
by reusing big1 and big2, pulling it out of the common package
and into ethash.

The commit also fixes chain maker to forward the uncle hash
when creating a simulated chain (it wasn't needed until now
so we just skipped a copy there).
This commit is contained in:
Péter Szilágyi 2017-06-29 13:13:00 +03:00
parent c4d28aee9b
commit 8c313eed26
No known key found for this signature in database
GPG Key ID: E9AE538CEDF8293D
2 changed files with 41 additions and 31 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

69
consensus/ethash/consensus.go
View File

@ -287,7 +287,7 @@ 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)
@ -301,33 +301,44 @@ 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)
// 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)
// holds intermediate values to make the algo easier to read & audit
x := new(big.Int)
y := new(big.Int)
// max(1 - (block_timestamp - parent_timestamp) // 10, -99)))
// (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 := new(big.Int).Div(parent.Difficulty, params.DifficultyBoundDivisor)
y.Div(parent.Difficulty, params.DifficultyBoundDivisor)
x.Mul(y, x)
x.Add(parent.Difficulty, x)
@ -335,19 +346,17 @@ func calcDifficultyMetropolis(time uint64, parent *types.Header) *big.Int {
if x.Cmp(params.MinimumDifficulty) < 0 {
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
}
@ -371,9 +380,9 @@ func calcDifficultyHomestead(time uint64, parent *types.Header) *big.Int {
// 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)
}
@ -387,14 +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
@ -421,12 +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),