forked from ethereum/go-ethereum
-
Notifications
You must be signed in to change notification settings - Fork 8
Commit
This commit does not belong to any branch on this repository, and may belong to a fork outside of the repository.
consensus/ethash: implement faster difficulty calculators (ethereum#2…
…1976) This PR adds re-written difficulty calculators, which are based on uint256. It also adds a fuzzer + oss-fuzz integration for the new fuzzer. It does differential fuzzing between the new and old calculators. Note: this PR does not actually enable the new calculators.
- Loading branch information
Showing
6 changed files
with
469 additions
and
0 deletions.
There are no files selected for viewing
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,193 @@ | ||
| // Copyright 2020 The go-ethereum Authors | ||
| // This file is part of the go-ethereum library. | ||
| // | ||
| // The go-ethereum library is free software: you can redistribute it and/or modify | ||
| // it under the terms of the GNU Lesser General Public License as published by | ||
| // the Free Software Foundation, either version 3 of the License, or | ||
| // (at your option) any later version. | ||
| // | ||
| // The go-ethereum library is distributed in the hope that it will be useful, | ||
| // but WITHOUT ANY WARRANTY; without even the implied warranty of | ||
| // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | ||
| // GNU Lesser General Public License for more details. | ||
| // | ||
| // You should have received a copy of the GNU Lesser General Public License | ||
| // along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>. | ||
|
|
||
| package ethash | ||
|
|
||
| import ( | ||
| "math/big" | ||
|
|
||
| "github.com/ethereum/go-ethereum/core/types" | ||
| "github.com/holiman/uint256" | ||
| ) | ||
|
|
||
| const ( | ||
| // frontierDurationLimit is for Frontier: | ||
| // The decision boundary on the blocktime duration used to determine | ||
| // whether difficulty should go up or down. | ||
| frontierDurationLimit = 13 | ||
| // minimumDifficulty The minimum that the difficulty may ever be. | ||
| minimumDifficulty = 131072 | ||
| // expDiffPeriod is the exponential difficulty period | ||
| expDiffPeriodUint = 100000 | ||
| // difficultyBoundDivisorBitShift is the bound divisor of the difficulty (2048), | ||
| // This constant is the right-shifts to use for the division. | ||
| difficultyBoundDivisor = 11 | ||
| ) | ||
|
|
||
| // CalcDifficultyFrontierU256 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 Frontier rules. | ||
| func CalcDifficultyFrontierU256(time uint64, parent *types.Header) *big.Int { | ||
| /* | ||
| Algorithm | ||
| block_diff = pdiff + pdiff / 2048 * (1 if time - ptime < 13 else -1) + int(2^((num // 100000) - 2)) | ||
| Where: | ||
| - pdiff = parent.difficulty | ||
| - ptime = parent.time | ||
| - time = block.timestamp | ||
| - num = block.number | ||
| */ | ||
|
|
||
| pDiff := uint256.NewInt() | ||
| pDiff.SetFromBig(parent.Difficulty) // pDiff: pdiff | ||
| adjust := pDiff.Clone() | ||
| adjust.Rsh(adjust, difficultyBoundDivisor) // adjust: pDiff / 2048 | ||
|
|
||
| if time-parent.Time < frontierDurationLimit { | ||
| pDiff.Add(pDiff, adjust) | ||
| } else { | ||
| pDiff.Sub(pDiff, adjust) | ||
| } | ||
| if pDiff.LtUint64(minimumDifficulty) { | ||
| pDiff.SetUint64(minimumDifficulty) | ||
| } | ||
| // 'pdiff' now contains: | ||
| // pdiff + pdiff / 2048 * (1 if time - ptime < 13 else -1) | ||
|
|
||
| if periodCount := (parent.Number.Uint64() + 1) / expDiffPeriodUint; periodCount > 1 { | ||
| // diff = diff + 2^(periodCount - 2) | ||
| expDiff := adjust.SetOne() | ||
| expDiff.Lsh(expDiff, uint(periodCount-2)) // expdiff: 2 ^ (periodCount -2) | ||
| pDiff.Add(pDiff, expDiff) | ||
| } | ||
| return pDiff.ToBig() | ||
| } | ||
|
|
||
| // CalcDifficultyHomesteadU256 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. | ||
| func CalcDifficultyHomesteadU256(time uint64, parent *types.Header) *big.Int { | ||
| /* | ||
| https://github.com/ethereum/EIPs/blob/master/EIPS/eip-2.md | ||
| Algorithm: | ||
| block_diff = pdiff + pdiff / 2048 * max(1 - (time - ptime) / 10, -99) + 2 ^ int((num / 100000) - 2)) | ||
| Our modification, to use unsigned ints: | ||
| block_diff = pdiff - pdiff / 2048 * max((time - ptime) / 10 - 1, 99) + 2 ^ int((num / 100000) - 2)) | ||
| Where: | ||
| - pdiff = parent.difficulty | ||
| - ptime = parent.time | ||
| - time = block.timestamp | ||
| - num = block.number | ||
| */ | ||
|
|
||
| pDiff := uint256.NewInt() | ||
| pDiff.SetFromBig(parent.Difficulty) // pDiff: pdiff | ||
| adjust := pDiff.Clone() | ||
| adjust.Rsh(adjust, difficultyBoundDivisor) // adjust: pDiff / 2048 | ||
|
|
||
| x := (time - parent.Time) / 10 // (time - ptime) / 10) | ||
| var neg = true | ||
| if x == 0 { | ||
| x = 1 | ||
| neg = false | ||
| } else if x >= 100 { | ||
| x = 99 | ||
| } else { | ||
| x = x - 1 | ||
| } | ||
| z := new(uint256.Int).SetUint64(x) | ||
| adjust.Mul(adjust, z) // adjust: (pdiff / 2048) * max((time - ptime) / 10 - 1, 99) | ||
| if neg { | ||
| pDiff.Sub(pDiff, adjust) // pdiff - pdiff / 2048 * max((time - ptime) / 10 - 1, 99) | ||
| } else { | ||
| pDiff.Add(pDiff, adjust) // pdiff + pdiff / 2048 * max((time - ptime) / 10 - 1, 99) | ||
| } | ||
| if pDiff.LtUint64(minimumDifficulty) { | ||
| pDiff.SetUint64(minimumDifficulty) | ||
| } | ||
| // for the exponential factor, a.k.a "the bomb" | ||
| // diff = diff + 2^(periodCount - 2) | ||
| if periodCount := (1 + parent.Number.Uint64()) / expDiffPeriodUint; periodCount > 1 { | ||
| expFactor := adjust.Lsh(adjust.SetOne(), uint(periodCount-2)) | ||
| pDiff.Add(pDiff, expFactor) | ||
| } | ||
| return pDiff.ToBig() | ||
| } | ||
|
|
||
| // MakeDifficultyCalculatorU256 creates a difficultyCalculator with the given bomb-delay. | ||
| // the difficulty is calculated with Byzantium rules, which differs from Homestead in | ||
| // how uncles affect the calculation | ||
| func MakeDifficultyCalculatorU256(bombDelay *big.Int) func(time uint64, parent *types.Header) *big.Int { | ||
| // Note, the calculations below looks at the parent number, which is 1 below | ||
| // the block number. Thus we remove one from the delay given | ||
| bombDelayFromParent := bombDelay.Uint64() - 1 | ||
| return func(time uint64, parent *types.Header) *big.Int { | ||
| /* | ||
| https://github.com/ethereum/EIPs/issues/100 | ||
| pDiff = parent.difficulty | ||
| BLOCK_DIFF_FACTOR = 9 | ||
| a = pDiff + (pDiff // BLOCK_DIFF_FACTOR) * adj_factor | ||
| b = min(parent.difficulty, MIN_DIFF) | ||
| child_diff = max(a,b ) | ||
| */ | ||
| x := (time - parent.Time) / 9 // (block_timestamp - parent_timestamp) // 9 | ||
| c := uint64(1) // if parent.unclehash == emptyUncleHashHash | ||
| if parent.UncleHash != types.EmptyUncleHash { | ||
| c = 2 | ||
| } | ||
| xNeg := x >= c | ||
| if xNeg { | ||
| // x is now _negative_ adjustment factor | ||
| x = x - c // - ( (t-p)/p -( 2 or 1) ) | ||
| } else { | ||
| x = c - x // (2 or 1) - (t-p)/9 | ||
| } | ||
| if x > 99 { | ||
| x = 99 // max(x, 99) | ||
| } | ||
| // parent_diff + (parent_diff / 2048 * max((2 if len(parent.uncles) else 1) - ((timestamp - parent.timestamp) // 9), -99)) | ||
| y := new(uint256.Int) | ||
| y.SetFromBig(parent.Difficulty) // y: p_diff | ||
| pDiff := y.Clone() // pdiff: p_diff | ||
| z := new(uint256.Int).SetUint64(x) //z : +-adj_factor (either pos or negative) | ||
| y.Rsh(y, difficultyBoundDivisor) // y: p__diff / 2048 | ||
| z.Mul(y, z) // z: (p_diff / 2048 ) * (+- adj_factor) | ||
|
|
||
| if xNeg { | ||
| y.Sub(pDiff, z) // y: parent_diff + parent_diff/2048 * adjustment_factor | ||
| } else { | ||
| y.Add(pDiff, z) // y: parent_diff + parent_diff/2048 * adjustment_factor | ||
| } | ||
| // minimum difficulty can ever be (before exponential factor) | ||
| if y.LtUint64(minimumDifficulty) { | ||
| y.SetUint64(minimumDifficulty) | ||
| } | ||
| // calculate a fake block number for the ice-age delay | ||
| // Specification: https://eips.ethereum.org/EIPS/eip-1234 | ||
| var pNum = parent.Number.Uint64() | ||
| if pNum >= bombDelayFromParent { | ||
| if fakeBlockNumber := pNum - bombDelayFromParent; fakeBlockNumber >= 2*expDiffPeriodUint { | ||
| z.SetOne() | ||
| z.Lsh(z, uint(fakeBlockNumber/expDiffPeriodUint-2)) | ||
| y.Add(z, y) | ||
| } | ||
| } | ||
| return y.ToBig() | ||
| } | ||
| } |
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,23 @@ | ||
| package main | ||
|
|
||
| import ( | ||
| "fmt" | ||
| "io/ioutil" | ||
| "os" | ||
|
|
||
| "github.com/ethereum/go-ethereum/tests/fuzzers/difficulty" | ||
| ) | ||
|
|
||
| func main() { | ||
| if len(os.Args) != 2 { | ||
| fmt.Fprintf(os.Stderr, "Usage: debug <file>") | ||
| os.Exit(1) | ||
| } | ||
| crasher := os.Args[1] | ||
| data, err := ioutil.ReadFile(crasher) | ||
| if err != nil { | ||
| fmt.Fprintf(os.Stderr, "error loading crasher %v: %v", crasher, err) | ||
| os.Exit(1) | ||
| } | ||
| difficulty.Fuzz(data) | ||
| } |
Oops, something went wrong.