Merge pull request #1578 from Gustav-Simonsson/frontier_thawing

miner: gas limit strategy, target 3141592 & def gas price 50 Shannon

1 files changed, 15 insertions, 2 deletions

diff --git a/core/chain_util.go b/core/chain_util.go
index 326bf13fb..104670195 100644
--- a/core/chain_util.go
+++ b/core/chain_util.go
@@ -69,17 +69,30 @@ func CalcTD(block, parent *types.Block) *big.Int {
 
 // CalcGasLimit computes the gas limit of the next block after parent.
 // The result may be modified by the caller.
+// This is miner strategy, not consensus protocol.
 func CalcGasLimit(parent *types.Block) *big.Int {
-	decay := new(big.Int).Div(parent.GasLimit(), params.GasLimitBoundDivisor)
+	// contrib = (parentGasUsed * 3 / 2) / 1024
 	contrib := new(big.Int).Mul(parent.GasUsed(), big.NewInt(3))
 	contrib = contrib.Div(contrib, big.NewInt(2))
 	contrib = contrib.Div(contrib, params.GasLimitBoundDivisor)
 
+	// decay = parentGasLimit / 1024 -1
+	decay := new(big.Int).Div(parent.GasLimit(), params.GasLimitBoundDivisor)
+	decay.Sub(decay, big.NewInt(1))
+
+	/*
+		strategy: gasLimit of block-to-mine is set based on parent's
+		gasUsed value.  if parentGasUsed > parentGasLimit * (2/3) then we
+		increase it, otherwise lower it (or leave it unchanged if it's right
+		at that usage) the amount increased/decreased depends on how far away
+		from parentGasLimit * (2/3) parentGasUsed is.
+	*/
 	gl := new(big.Int).Sub(parent.GasLimit(), decay)
 	gl = gl.Add(gl, contrib)
-	gl = gl.Add(gl, big.NewInt(1))
 	gl.Set(common.BigMax(gl, params.MinGasLimit))
 
+	// however, if we're now below the target (GenesisGasLimit) we increase the
+	// limit as much as we can (parentGasLimit / 1024 -1)
 	if gl.Cmp(params.GenesisGasLimit) < 0 {
 		gl.Add(parent.GasLimit(), decay)
 		gl.Set(common.BigMin(gl, params.GenesisGasLimit))