core/block_validator.go#calcDifficultyAtlantis is wrong

[meowsbits]

https://github.com/eth-classic/go-ethereum/blob/development/core/block_validator.go#L362

At first review this appears to use a hardcoded bomb delay value according to EIP1234, which is not relevant to ETC nor Atlantis.

Atlantis occurs canonically after ECIP1010 (difficulty bomb defuse), which makes this spec and logic inapplicable.

func calcDifficultyAtlantis(time uint64, parent *types.Header) *big.Int {
	bombDelayFromParent := new(big.Int).Sub(big.NewInt(3000000), big1)
	// 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 := parent.Time

	// holds intermediate values to make the algo easier to read & audit
	x := new(big.Int)
	y := new(big.Int)

	// (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((2 if len(parent.uncles) else 1) - ((timestamp - parent.timestamp) // 9), -99))
	y.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)
	}
	// calculate a fake block number for the ice-age delay
	// Specification: https://eips.ethereum.org/EIPS/eip-1234
	fakeBlockNumber := new(big.Int)
	if parent.Number.Cmp(bombDelayFromParent) >= 0 {
		fakeBlockNumber = fakeBlockNumber.Sub(parent.Number, bombDelayFromParent)
	}
	// for the exponential factor
	periodCount := fakeBlockNumber
	periodCount.Div(periodCount, expDiffPeriod)

	// the exponential factor, commonly referred to as "the bomb"
	// diff = diff + 2^(periodCount - 2)
	if periodCount.Cmp(big1) > 0 {
		y.Sub(periodCount, big2)
		y.Exp(big2, y, nil)
		x.Add(x, y)
	}
	return x
}

[meowsbits]

Only EIP100 should be introduced.

[austinabell]

yeah adding the bomb delay segment was because I wasn't aware ETC defused the difficulty bomb when adding that in (ETC has an equivalent of the EIPs you mentioned) and I wanted to make sure the client stayed in sync with other clients (as other clients had this value in) Very minor change as it doesn't affect anything really but I'll have a PR in soon

[meowsbits]

Very minor change as it doesn't affect anything really

At block 11,500,000 (or fork number + 3000000) the network would have forked if this client were in play. Block difficulty is a consensus issue.

Although yes, the fix is simple.

[austinabell]

Yeah another case of not choosing my words carefully, I meant to say it wasn't an urgent PR since those blocks are so incredibly far in the future (In reference to the testnet we have running and the timeline of the PR).

[meowsbits]

>>> 3000000 * 14

  3000000 × 14

   = 42000000

>>> ans / 60 / 60 / 24

  ((ans / 60) / 60) / 24

   = 486.111

where 14 is approximate average block time seconds

**~ 486 days**

incredibly far in the future

is more like "the next few decades", eg.

• ECIP 1017: Different behaviour for go-ethereum and Parity openethereum/parity-ethereum#6523
• ECIP-1017 ETC monetary policy and emission schedule ethereumproject/ECIPs#15 (comment)

[GregTheGreek]

>>> 3000000 * 14

  3000000 × 14

   = 42000000

>>> ans / 60 / 60 / 24

  ((ans / 60) / 60) / 24

   = 486.111

where 14 is approximate average block time seconds

**~ 486 days**

incredibly far in the future

is more like "the next few decades", eg.

• paritytech/parity-ethereum#6523
• ethereumproject/ECIPs#15 (comment)

May we please revert back to testing and less on semantics. Thank you for identifying the bug, we're working on it 😄

[soc1c]

Done #69