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authorJeffrey Wilcke <jeffrey@ethereum.org>2017-06-30 21:39:18 +0800
committerPéter Szilágyi <peterke@gmail.com>2017-06-30 21:41:25 +0800
commitc4d28aee9bb3ce7851e92462bb2e7fdbf88f9a9a (patch)
tree9b2dd9aa2446d7db8ed8f06f4469648839928b0d
parenta0aa071ca6f6bfd77fb57273ef5477d3aa2ac6c0 (diff)
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consensus/ethash: implement Metropolis EIP 100
-rw-r--r--consensus/ethash/consensus.go48
1 files changed, 48 insertions, 0 deletions
diff --git a/consensus/ethash/consensus.go b/consensus/ethash/consensus.go
index dd9c81fd4..fa2d740e4 100644
--- a/consensus/ethash/consensus.go
+++ b/consensus/ethash/consensus.go
@@ -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 {
next := new(big.Int).Add(parent.Number, common.Big1)
switch {
+ case config.IsMetropolis(next):
+ return calcDifficultyMetropolis(time, parent)
case config.IsHomestead(next):
return calcDifficultyHomestead(time, parent)
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.
var (
expDiffPeriod = big.NewInt(100000)
+ big9 = big.NewInt(9)
big10 = big.NewInt(10)
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
// 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.