fork

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 Go to latest Published: Dec 28, 2019 License: Unlicense Imports: 17 Imported by: 0

Documentation

Overview

Package fork handles tracking the hard fork status and is used to determine which consensus rules apply on a block

Index

Constants

This section is empty.

Variables

View Source 
var (
	// FirstPowLimit is
	FirstPowLimit = func() big.Int {
		mplb, _ := hex.DecodeString(
			"0fffff0000000000000000000000000000000000000000000000000000000000")
		return *big.NewInt(0).SetBytes(mplb)
	}()
	// FirstPowLimitBits is
	FirstPowLimitBits = BigToCompact(&FirstPowLimit)
	// IsTestnet is set at startup here to be accessible to all other libraries
	IsTestnet bool
	// List is the list of existing hard forks and when they activate
	List = []HardForks{
		{
			Number:             0,
			Name:               "Inception",
			ActivationHeight:   0,
			Algos:              P9Algos,
			AlgoVers:           P9AlgoVers,
			TargetTimePerBlock: 36,
			AveragingInterval:  3600,
			TestnetStart:       1,
		},
	}
	// P9AlgoVers is the lookup for after 1st hardfork
	P9AlgoVers = map[int32]string{
		5:  "blake2b",
		6:  "argon2i",
		7:  "cn7v2",
		8:  "keccak",
		9:  "scrypt",
		10: "sha256d",
		11: "skein",
		12: "stribog",
		13: "lyra2rev2",
	}
	// P9Algos is the algorithm specifications after the hard fork
	// given ns/op values are approximate and kopach bench writes them to
	// a file. These should vary on different architectures due to limitations
	// of division bit width and the cache behavior of hash functions, and
	// refers to one thread of execution, how this relates to number of cores
	// will vary also
	P9Algos = map[string]AlgoParams{
		P9AlgoVers[5]:  {0, FirstPowLimitBits},
		P9AlgoVers[6]:  {1, FirstPowLimitBits},
		P9AlgoVers[7]:  {2, FirstPowLimitBits},
		P9AlgoVers[8]:  {3, FirstPowLimitBits},
		P9AlgoVers[9]:  {4, FirstPowLimitBits},
		P9AlgoVers[10]: {5, FirstPowLimitBits},
		P9AlgoVers[11]: {6, FirstPowLimitBits},
		P9AlgoVers[12]: {7, FirstPowLimitBits},
		P9AlgoVers[13]: {8, FirstPowLimitBits},
	}
	// SecondPowLimit is
	SecondPowLimit = func() big.Int {
		mplb, _ := hex.DecodeString(
			"001f1f1f1f1f1f1f1f1f1f1f1f1f1f1f1f1f1f1f1f1f1f1f1f1f1f1f1f1f1f1f")
		return *big.NewInt(0).SetBytes(mplb)
	}()
	SecondPowLimitBits = BigToCompact(&SecondPowLimit)
	MainPowLimit       = func() big.Int {
		mplb, _ := hex.DecodeString(
			"00000fffff000000000000000000000000000000000000000000000000000000")
		return *big.NewInt(0).SetBytes(mplb)
	}()
	MainPowLimitBits = BigToCompact(&MainPowLimit)
)
View Source 
var HashReps = 2

HashReps allows the number of multiplication/division cycles to be repeated before the final hash, on release for mainnet this is probably set to 9 or so to raise the difficulty to a reasonable level for the hard fork. at 5 repetitions (first plus repeats, thus 4), an example block header produces a number around 48kb in byte size and ~119000 decimal digits, which is then finally hashed down to 32 bytes

Functions

func Argon2i 

func Argon2i(bytes []byte) []byte

Argon2i takes bytes, generates a Lyra2REv2 hash as salt, generates an argon2i key

func BigToCompact 

func BigToCompact(n *big.Int) uint32

BigToCompact converts a whole number N to a compact representation using an unsigned 32-bit number. The compact representation only provides 23 bits of precision, so values larger than (2^23 - 1) only encode the most significant digits of the number. See CompactToBig for details.

func Blake14lr 

func Blake14lr(bytes []byte) []byte

Blake14lr takes bytes and returns a blake14lr 256 bit hash

func Blake2b 

func Blake2b(bytes []byte) []byte

Blake2b takes bytes and returns a blake2b 256 bit hash

func Blake2s 

func Blake2s(bytes []byte) []byte

Blake2s takes bytes and returns a blake2s 256 bit hash

func CompactToBig 

func CompactToBig(compact uint32) *big.Int

CompactToBig converts a compact representation of a whole number N to an unsigned 32-bit number. The representation is similar to IEEE754 floating point numbers. Like IEEE754 floating point, there are three basic components: the sign, the exponent, and the mantissa. They are broken out as follows:

  • the most significant 8 bits represent the unsigned base 256 exponent
  • bit 23 (the 24th bit) represents the sign bit
  • the least significant 23 bits represent the mantissa ------------------------------------------------- | Exponent | Sign | Mantissa | ------------------------------------------------- | 8 bits [31-24] | 1 bit [23] | 23 bits [22-00] | -------------------------------------------------

The formula to calculate N is: 

N = (-1^sign) * mantissa * 256^(exponent-3)

This compact form is only used in bitcoin to encode unsigned 256-bit numbers which represent difficulty targets, thus there really is not a need for a sign bit, but it is implemented here to stay consistent with bitcoind.

func Cryptonight7v2 

func Cryptonight7v2(bytes []byte) []byte

Cryptonight7v2 takes bytes and returns a cryptonight 7 v2 256 bit hash

func DivHash 

func DivHash(hf func([]byte) []byte, blockbytes []byte, howmany int) []byte

DivHash first runs an arbitrary big number calculation involving a very large integer, and hashes the result. In this way, this hash requires both one of 9 arbitrary hash functions plus a big number long division operation and three multiplication operations, unlikely to be satisfied on anything other than CPU and GPU, with contrary advantages on each - GPU division is 32 bits wide operations, CPU is 64, but GPU hashes about equal to a CPU to varying degrees of memory hardness (and CPU cache size then improves CPU performance at some hashes)

This hash generates very large random numbers from an 80 byte block using a procedure involving two squares of recombined spliced halves, multiplied together and then divided by the original block, reversed, repeated 4 more times, of over 48kb to represent the product, which is hashed afterwards. ( see example in fork/scratch/divhash.go )

This would be around half of the available level 1 cache of a ryzen 5 1600, likely distributed as 6 using the 64kb and 3 threads using the 32kb smaller ones. Here is a block diagram of Zen architecture: https://en.wikichip.org/w/images/thumb/0/02/zen_block_diagram.svg/1178px-zen_block_diagram.svg.png This is one, with Zen the cores are independently partitioned. But it shows that it has one divider per core. Thus for a 6 core, 6 would be the right number to use with it as other numbers will lead to contention and memory copies. Probably its ability to branch twice per cycle will be a big boost for its performance in this task.

Long division units are expensive and slow, and make a perfect application specific proof of work because a substantial part of the cost as proportional to the relative surface area of circuitry it is substantially more than 10% of the total logic on a CPU. There is low chances of putting these units into one package with half half IDIV and IMUL units and enough cache for each one, would be economic or accessible to most chip manufacturers at a scale and clock that beats the CPU price.

Most GPUs still only have 32 bit integer divide units because the type of mathematics done by GPUs is mainly based on multiplication, addition and subtraction, specifically, with matrixes, which are per-bit equivalent to big (128-512 bit) addition, built for walking graphs and generating directional or particle effects, under gravity, and the like. Video is very parallelisable so generally speaking GPU's main bulk of processing capability does not help here, caches holding a fraction of the number at a time as it is computed, and only 32 bits wide at a time for the special purpose dividers, that are relatively swamped by stream processors in big grids.

The cheaper arithmetic units can be programmed to also perform the calculations but they are going to be funny letter log differences to the point it adds up to less than 10% better due to complexity of the code and scheduling it.

Long story short, this hash function should be the end of big margin ASIC mining, and a lot of R&D funds going to improving smaller fabs for spewing out such processors.

func GetAlgoName 

func GetAlgoName(algoVer int32, height int32) (name string)

GetAlgoName returns the string identifier of an algorithm depending on hard fork activation status

func GetAlgoVer 

func GetAlgoVer(name string, height int32) (version int32)

GetAlgoVer returns the version number for a given algorithm (by string name) at a given height. If "random" is given, a random number is taken from the system secure random source (for randomised cpu mining)

func GetAveragingInterval 

func GetAveragingInterval(height int32) (r int64)

GetAveragingInterval returns the active block interval target based on hard fork status

func GetCurrent 

func GetCurrent(height int32) (curr int)

GetCurrent returns the hardfork number code

func GetMinBits 

func GetMinBits(algoname string, height int32) (mb uint32)

GetMinBits returns the minimum diff bits based on height and testnet

func GetMinDiff 

func GetMinDiff(algoname string, height int32) (md *big.Int)

GetMinDiff returns the minimum difficulty in uint256 form

func GetTargetTimePerBlock 

func GetTargetTimePerBlock(height int32) (r int64)

GetTargetTimePerBlock returns the active block interval target based on hard fork status

func Hash 

func Hash(bytes []byte, name string, height int32) (out chainhash.Hash)

Hash computes the hash of bytes using the named hash

func Keccak 

func Keccak(bytes []byte) []byte

Keccak takes bytes and returns a keccak (sha-3) 256 bit hash

func Lyra2REv2 

func Lyra2REv2(bytes []byte) []byte

Lyra2REv2 takes bytes and returns a lyra2rev2 256 bit hash

func SHA256D 

func SHA256D(bytes []byte) []byte

SHA256D takes bytes and returns a double SHA256 hash

func Scrypt 

func Scrypt(bytes []byte) []byte

Scrypt takes bytes and returns a scrypt 256 bit hash

func Skein 

func Skein(bytes []byte) []byte

Skein takes bytes and returns a skein 256 bit hash

func Stribog 

func Stribog(bytes []byte) []byte

Stribog takes bytes and returns a double GOST Stribog 256 bit hash

Types

type AlgoParams 

type AlgoParams struct {
	Version int32
	MinBits uint32
}

AlgoParams are the identifying block version number and their minimum target bits

type HardForks 

type HardForks struct {
	Number             uint32
	ActivationHeight   int32
	Name               string
	Algos              map[string]AlgoParams
	AlgoVers           map[int32]string
	TargetTimePerBlock int32
	AveragingInterval  int64
	TestnetStart       int32
}

HardForks is the details related to a hard fork, number, name and activation height

Source Files

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