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consensus/misc: reduce allocations and improve comments in CalcBaseFee #24958

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merged 2 commits into from Jun 2, 2022
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consensus/misc: reduce allocations and improve comments in CalcBaseFee #24958

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1fe322f
consensus/misc: reduce allocations in CalcBaseFee
Jeiwan May 26, 2022
005fb1b
consensus/misc: add formulas of CalcBaseFee
Jeiwan May 26, 2022
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42 changes: 21 additions & 21 deletions consensus/misc/eip1559.go
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Expand Up @@ -58,36 +58,36 @@ func CalcBaseFee(config *params.ChainConfig, parent *types.Header) *big.Int {
return new(big.Int).SetUint64(params.InitialBaseFee)
}

var (
parentGasTarget = parent.GasLimit / params.ElasticityMultiplier
parentGasTargetBig = new(big.Int).SetUint64(parentGasTarget)
baseFeeChangeDenominator = new(big.Int).SetUint64(params.BaseFeeChangeDenominator)
)
parentGasTarget := parent.GasLimit / params.ElasticityMultiplier
// If the parent gasUsed is the same as the target, the baseFee remains unchanged.
if parent.GasUsed == parentGasTarget {
return new(big.Int).Set(parent.BaseFee)
}

var (
num = new(big.Int)
denom = new(big.Int)
)

if parent.GasUsed > parentGasTarget {
// If the parent block used more gas than its target, the baseFee should increase.
gasUsedDelta := new(big.Int).SetUint64(parent.GasUsed - parentGasTarget)
x := new(big.Int).Mul(parent.BaseFee, gasUsedDelta)
y := x.Div(x, parentGasTargetBig)
baseFeeDelta := math.BigMax(
x.Div(y, baseFeeChangeDenominator),
common.Big1,
)
// max(1, parentBaseFee * gasUsedDelta / parentGasTarget / baseFeeChangeDenominator)
num.SetUint64(parent.GasUsed - parentGasTarget)
num.Mul(num, parent.BaseFee)
num.Div(num, denom.SetUint64(parentGasTarget))
num.Div(num, denom.SetUint64(params.BaseFeeChangeDenominator))
baseFeeDelta := math.BigMax(num, common.Big1)

return x.Add(parent.BaseFee, baseFeeDelta)
return num.Add(parent.BaseFee, baseFeeDelta)
} else {
// Otherwise if the parent block used less gas than its target, the baseFee should decrease.
gasUsedDelta := new(big.Int).SetUint64(parentGasTarget - parent.GasUsed)
x := new(big.Int).Mul(parent.BaseFee, gasUsedDelta)
y := x.Div(x, parentGasTargetBig)
baseFeeDelta := x.Div(y, baseFeeChangeDenominator)
// max(0, parentBaseFee * gasUsedDelta / parentGasTarget / baseFeeChangeDenominator)
num.SetUint64(parentGasTarget - parent.GasUsed)
num.Mul(num, parent.BaseFee)
num.Div(num, denom.SetUint64(parentGasTarget))
num.Div(num, denom.SetUint64(params.BaseFeeChangeDenominator))
baseFee := num.Sub(parent.BaseFee, num)

return math.BigMax(
x.Sub(parent.BaseFee, baseFeeDelta),
common.Big0,
)
return math.BigMax(baseFee, common.Big0)
}
}