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consensus/ethash: shuffle func calc*Size comments around

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This commit is contained in:
Felix Lange 2018-01-12 12:57:59 +01:00
parent 15d0c9bcd7
commit 0326bb8824
1 changed files with 10 additions and 11 deletions
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21
consensus/ethash/algorithm_go1.8.go
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@ -20,20 +20,19 @@ package ethash
import "math/big"
// cacheSize calculates and returns the size of the ethash verification cache that
// belongs to a certain block number. The cache size grows linearly, however, we
// always take the highest prime below the linearly growing threshold in order to
// reduce the risk of accidental regularities leading to cyclic behavior.
// cacheSize returns the size of the ethash verification cache that belongs to a certain
// block number.
func cacheSize(block uint64) uint64 {
// If we have a pre-generated value, use that
epoch := int(block / epochLength)
if epoch < maxEpoch {
return cacheSizes[epoch]
}
// No known cache size, calculate manually (sanity branch only)
return calcCacheSize(epoch)
}
// calcCacheSize calculates the cache size for epoch. The cache size grows linearly,
// however, we always take the highest prime below the linearly growing threshold in order
// to reduce the risk of accidental regularities leading to cyclic behavior.
func calcCacheSize(epoch int) uint64 {
size := cacheInitBytes + cacheGrowthBytes*uint64(epoch) - hashBytes
for !new(big.Int).SetUint64(size / hashBytes).ProbablyPrime(1) { // Always accurate for n < 2^64
@ -42,12 +41,9 @@ func calcCacheSize(epoch int) uint64 {
return size
}
// datasetSize calculates and returns the size of the ethash mining dataset that
// belongs to a certain block number. The dataset size grows linearly, however, we
// always take the highest prime below the linearly growing threshold in order to
// reduce the risk of accidental regularities leading to cyclic behavior.
// datasetSize returns the size of the ethash mining dataset that belongs to a certain
// block number.
func datasetSize(block uint64) uint64 {
// If we have a pre-generated value, use that
epoch := int(block / epochLength)
if epoch < len(datasetSizes) {
return datasetSizes[epoch]
@ -55,6 +51,9 @@ func datasetSize(block uint64) uint64 {
return calcDatasetSize(epoch)
}
// calcDatasetSize calculates the dataset size for epoch. The dataset size grows linearly,
// however, we always take the highest prime below the linearly growing threshold in order
// to reduce the risk of accidental regularities leading to cyclic behavior.
func calcDatasetSize(epoch int) uint64 {
size := datasetInitBytes + datasetGrowthBytes*uint64(epoch) - mixBytes
for !new(big.Int).SetUint64(size / mixBytes).ProbablyPrime(1) { // Always accurate for n < 2^64