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[lbry] blockchain: change the difficulty adjustment algorithm.

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adjusted := target + (actual - target) / 8

  max := target + (target / 2)
  min := target - (target / 8)

  if adjusted > max {
    adjusted = max
  } else if adj < min {
    adjusted = min
  }

  diffculty := lastDifficulty * adjusted / target
This commit is contained in:
Roy Lee 2018-06-12 17:27:22 -07:00
parent c8abd8fe93
commit 8591f960e2
2 changed files with 28 additions and 33 deletions
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5
blockchain/chain.go
View file

@ -1736,7 +1736,6 @@ func New(config *Config) (*BlockChain, error) {
params := config.ChainParams
targetTimespan := int64(params.TargetTimespan / time.Second)
targetTimePerBlock := int64(params.TargetTimePerBlock / time.Second)
adjustmentFactor := params.RetargetAdjustmentFactor
b := BlockChain{
checkpoints: config.Checkpoints,
checkpointsByHeight: checkpointsByHeight,
@ -1745,8 +1744,8 @@ func New(config *Config) (*BlockChain, error) {
timeSource: config.TimeSource,
sigCache: config.SigCache,
indexManager: config.IndexManager,
minRetargetTimespan: targetTimespan / adjustmentFactor,
maxRetargetTimespan: targetTimespan * adjustmentFactor,
minRetargetTimespan: targetTimespan - (targetTimespan / 8),
maxRetargetTimespan: targetTimespan + (targetTimespan / 2),
blocksPerRetarget: int32(targetTimespan / targetTimePerBlock),
index: newBlockIndex(config.DB, params),
hashCache: config.HashCache,

26
blockchain/difficulty.go
View file

@ -159,7 +159,6 @@ func CalcWork(bits uint32) *big.Int {
func (b *BlockChain) calcEasiestDifficulty(bits uint32, duration time.Duration) uint32 {
// Convert types used in the calculations below.
durationVal := int64(duration / time.Second)
adjustmentFactor := big.NewInt(b.chainParams.RetargetAdjustmentFactor)
// The test network rules allow minimum difficulty blocks after more
// than twice the desired amount of time needed to generate a block has
@ -178,7 +177,8 @@ func (b *BlockChain) calcEasiestDifficulty(bits uint32, duration time.Duration)
// multiplied by the max adjustment factor.
newTarget := CompactToBig(bits)
for durationVal > 0 && newTarget.Cmp(b.chainParams.PowLimit) < 0 {
newTarget.Mul(newTarget, adjustmentFactor)
adj := new(big.Int).Div(newTarget, big.NewInt(2))
newTarget.Add(newTarget, adj)
durationVal -= b.maxRetargetTimespan
}
@ -224,9 +224,6 @@ func (b *BlockChain) calcNextRequiredDifficulty(lastNode *blockNode, newBlockTim
return b.chainParams.PowLimitBits, nil
}
// Return the previous block's difficulty requirements if this block
// is not at a difficulty retarget interval.
if (lastNode.height+1)%b.blocksPerRetarget != 0 {
// For networks that support it, allow special reduction of the
// required difficulty once too much time has elapsed without
// mining a block.
@ -246,25 +243,25 @@ func (b *BlockChain) calcNextRequiredDifficulty(lastNode *blockNode, newBlockTim
return b.findPrevTestNetDifficulty(lastNode), nil
}
// For the main network (or any unrecognized networks), simply
// return the previous block's difficulty requirements.
return lastNode.bits, nil
}
// Get the block node at the previous retarget (targetTimespan days
// worth of blocks).
firstNode := lastNode.RelativeAncestor(b.blocksPerRetarget - 1)
firstNode := lastNode.RelativeAncestor(b.blocksPerRetarget)
if lastNode.height == 0 {
firstNode = lastNode
}
if firstNode == nil {
return 0, AssertError("unable to obtain previous retarget block")
}
targetTimeSpan := int64(b.chainParams.TargetTimespan / time.Second)
// Limit the amount of adjustment that can occur to the previous
// difficulty.
actualTimespan := lastNode.timestamp - firstNode.timestamp
adjustedTimespan := actualTimespan
if actualTimespan < b.minRetargetTimespan {
adjustedTimespan := targetTimeSpan + (actualTimespan-targetTimeSpan)/8
if adjustedTimespan < b.minRetargetTimespan {
adjustedTimespan = b.minRetargetTimespan
} else if actualTimespan > b.maxRetargetTimespan {
} else if adjustedTimespan > b.maxRetargetTimespan {
adjustedTimespan = b.maxRetargetTimespan
}
@ -275,7 +272,6 @@ func (b *BlockChain) calcNextRequiredDifficulty(lastNode *blockNode, newBlockTim
// result.
oldTarget := CompactToBig(lastNode.bits)
newTarget := new(big.Int).Mul(oldTarget, big.NewInt(adjustedTimespan))
targetTimeSpan := int64(b.chainParams.TargetTimespan / time.Second)
newTarget.Div(newTarget, big.NewInt(targetTimeSpan))
// Limit new value to the proof of work limit.