Documentation
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Index ¶
- Variables
- func Argon2i(bytes []byte) []byte
- func Blake2b(bytes []byte) []byte
- func Blake3(bytes []byte) []byte
- func DivHash(hf func([]byte) []byte, blockbytes []byte, howmany int) []byte
- func Hash(bytes []byte, name string, height int32) (out chainhash.Hash)
- func Keccak(bytes []byte) []byte
- func ScryptHash(bytes []byte) []byte
- func Skein(bytes []byte) []byte
- func Stribog(bytes []byte) []byte
- func X11(bytes []byte) (out []byte)
Constants ¶
This section is empty.
Variables ¶
var F, E, W, I, D, T logg.LevelPrinter = logg.GetLogPrinterSet(subsystem)
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 DivHash ¶
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 ScryptHash ¶
ScryptHash takes bytes and returns a scrypt 256 bit hash
Types ¶
This section is empty.
Source Files
