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@@ -22,7 +22,9 @@ import (
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"errors"
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"fmt"
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"io/ioutil"
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+ "math"
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"math/big"
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+ "math/rand"
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"os"
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"path/filepath"
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"sync"
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@@ -46,7 +48,7 @@ var (
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maxUint256 = new(big.Int).Exp(big.NewInt(2), big.NewInt(256), big.NewInt(0))
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// sharedEthash is a full instance that can be shared between multiple users.
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- sharedEthash = NewFullEthash("", 3, 0, "", 0)
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+ sharedEthash = NewFullEthash("", 3, 0, "", 1, 0)
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// algorithmRevision is the data structure version used for file naming.
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algorithmRevision = 23
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@@ -64,13 +66,13 @@ type cache struct {
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lock sync.Mutex // Ensures thread safety for updating the usage time
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}
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-// generate ensures that the cache content is generates.
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+// generate ensures that the cache content is generated before use.
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func (c *cache) generate(dir string, limit int, test bool) {
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c.once.Do(func() {
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// If we have a testing cache, generate and return
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if test {
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rawCache := generateCache(1024, seedHash(c.epoch*epochLength+1))
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- c.cache = prepare(uint64(len(rawCache)), bytes.NewReader(rawCache))
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+ c.cache = prepare(1024, bytes.NewReader(rawCache))
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return
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}
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// Full cache generation is needed, check cache dir for existing data
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@@ -117,25 +119,112 @@ func (c *cache) generate(dir string, limit int, test bool) {
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})
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}
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+// dataset wraps an ethash dataset with some metadata to allow easier concurrent use.
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+type dataset struct {
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+ epoch uint64 // Epoch for which this cache is relevant
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+ dataset []uint32 // The actual cache data content
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+ used time.Time // Timestamp of the last use for smarter eviction
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+ once sync.Once // Ensures the cache is generated only once
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+ lock sync.Mutex // Ensures thread safety for updating the usage time
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+}
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+
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+// generate ensures that the dataset content is generated before use.
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+func (d *dataset) generate(dir string, limit int, test bool, discard bool) {
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+ d.once.Do(func() {
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+ // If we have a testing dataset, generate and return
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+ if test {
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+ rawCache := generateCache(1024, seedHash(d.epoch*epochLength+1))
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+ intCache := prepare(1024, bytes.NewReader(rawCache))
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+
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+ rawDataset := generateDataset(32*1024, intCache)
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+ d.dataset = prepare(32*1024, bytes.NewReader(rawDataset))
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+
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+ return
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+ }
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+ // Full dataset generation is needed, check dataset dir for existing data
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+ csize := cacheSize(d.epoch*epochLength + 1)
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+ dsize := datasetSize(d.epoch*epochLength + 1)
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+ seed := seedHash(d.epoch*epochLength + 1)
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+
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+ path := filepath.Join(dir, fmt.Sprintf("full-R%d-%x", algorithmRevision, seed))
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+ logger := log.New("seed", hexutil.Bytes(seed))
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+
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+ if dir != "" {
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+ dump, err := os.Open(path)
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+ if err == nil {
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+ if !discard {
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+ logger.Info("Loading ethash DAG from disk")
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+ start := time.Now()
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+ d.dataset = prepare(dsize, bufio.NewReader(dump))
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+ logger.Info("Loaded ethash DAG from disk", "elapsed", common.PrettyDuration(time.Since(start)))
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+ }
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+ dump.Close()
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+ return
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+ }
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+ }
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+ // No previous disk dataset was available, generate on the fly
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+ rawCache := generateCache(csize, seed)
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+ intCache := prepare(csize, bytes.NewReader(rawCache))
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+
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+ rawDataset := generateDataset(dsize, intCache)
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+ if !discard {
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+ d.dataset = prepare(dsize, bytes.NewReader(rawDataset))
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+ }
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+ // If a dataset directory is given, attempt to serialize for next time
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+ if dir != "" {
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+ // Store the ethash dataset to disk
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+ start := time.Now()
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+ if err := os.MkdirAll(filepath.Dir(path), os.ModePerm); err != nil {
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+ logger.Error("Failed to create ethash DAG dir", "err", err)
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+ } else if err := ioutil.WriteFile(path, rawDataset, os.ModePerm); err != nil {
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+ logger.Error("Failed to write ethash DAG to disk", "err", err)
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+ } else {
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+ logger.Info("Stored ethash DAG to disk", "elapsed", common.PrettyDuration(time.Since(start)))
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+ }
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+ // Iterate over all previous instances and delete old ones
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+ for ep := int(d.epoch) - limit; ep >= 0; ep-- {
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+ seed := seedHash(uint64(ep)*epochLength + 1)
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+ path := filepath.Join(dir, fmt.Sprintf("full-R%d-%x", algorithmRevision, seed))
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+ os.Remove(path)
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+ }
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+ }
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+ })
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+}
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+
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+// MakeCache generates a new ethash cache and optionally stores it to disk.
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+func MakeCache(block uint64, dir string) {
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+ c := cache{epoch: block/epochLength + 1}
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+ c.generate(dir, math.MaxInt32, false)
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+}
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+
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+// MakeDataset generates a new ethash dataset and optionally stores it to disk.
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+func MakeDataset(block uint64, dir string) {
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+ d := dataset{epoch: block/epochLength + 1}
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+ d.generate(dir, math.MaxInt32, false, true)
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+}
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+
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// Ethash is a PoW data struture implementing the ethash algorithm.
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type Ethash struct {
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cachedir string // Data directory to store the verification caches
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cachesinmem int // Number of caches to keep in memory
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cachesondisk int // Number of caches to keep on disk
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dagdir string // Data directory to store full mining datasets
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+ dagsinmem int // Number of mining datasets to keep in memory
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dagsondisk int // Number of mining datasets to keep on disk
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- caches map[uint64]*cache // In memory caches to avoid regenerating too often
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- future *cache // Pre-generated cache for the estimated future epoch
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- lock sync.Mutex // Ensures thread safety for the in-memory caches
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+ caches map[uint64]*cache // In memory caches to avoid regenerating too often
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+ fcache *cache // Pre-generated cache for the estimated future epoch
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+ datasets map[uint64]*dataset // In memory datasets to avoid regenerating too often
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+ fdataset *dataset // Pre-generated dataset for the estimated future epoch
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+ lock sync.Mutex // Ensures thread safety for the in-memory caches
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- hashrate *metrics.StandardMeter // Meter tracking the average hashrate
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+ hashrate metrics.Meter // Meter tracking the average hashrate
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tester bool // Flag whether to use a smaller test dataset
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}
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// NewFullEthash creates a full sized ethash PoW scheme.
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-func NewFullEthash(cachedir string, cachesinmem, cachesondisk int, dagdir string, dagsondisk int) PoW {
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+func NewFullEthash(cachedir string, cachesinmem, cachesondisk int, dagdir string, dagsinmem, dagsondisk int) PoW {
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if cachesinmem <= 0 {
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log.Warn("One ethash cache must alwast be in memory", "requested", cachesinmem)
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cachesinmem = 1
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@@ -151,8 +240,11 @@ func NewFullEthash(cachedir string, cachesinmem, cachesondisk int, dagdir string
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cachesinmem: cachesinmem,
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cachesondisk: cachesondisk,
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dagdir: dagdir,
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+ dagsinmem: dagsinmem,
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dagsondisk: dagsondisk,
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caches: make(map[uint64]*cache),
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+ datasets: make(map[uint64]*dataset),
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+ hashrate: metrics.NewMeter(),
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}
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}
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@@ -162,7 +254,9 @@ func NewTestEthash() PoW {
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return &Ethash{
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cachesinmem: 1,
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caches: make(map[uint64]*cache),
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+ datasets: make(map[uint64]*dataset),
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tester: true,
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+ hashrate: metrics.NewMeter(),
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}
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}
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@@ -181,7 +275,7 @@ func (ethash *Ethash) Verify(block Block) error {
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// Go < 1.7 cannot calculate new cache/dataset sizes (no fast prime check)
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return ErrNonceOutOfRange
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}
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- // Ensure twe have a valid difficulty for the block
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+ // Ensure that we have a valid difficulty for the block
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difficulty := block.Difficulty()
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if difficulty.Sign() <= 0 {
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return ErrInvalidDifficulty
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@@ -228,9 +322,9 @@ func (ethash *Ethash) cache(block uint64) []uint32 {
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log.Debug("Evicted ethash cache", "epoch", evict.epoch, "used", evict.used)
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}
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// If we have the new cache pre-generated, use that, otherwise create a new one
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- if ethash.future != nil && ethash.future.epoch == epoch {
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+ if ethash.fcache != nil && ethash.fcache.epoch == epoch {
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log.Debug("Using pre-generated cache", "epoch", epoch)
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- current, ethash.future = ethash.future, nil
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+ current, ethash.fcache = ethash.fcache, nil
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} else {
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log.Debug("Requiring new ethash cache", "epoch", epoch)
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current = &cache{epoch: epoch}
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@@ -238,10 +332,10 @@ func (ethash *Ethash) cache(block uint64) []uint32 {
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ethash.caches[epoch] = current
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// If we just used up the future cache, or need a refresh, regenerate
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- if ethash.future == nil || ethash.future.epoch <= epoch {
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+ if ethash.fcache == nil || ethash.fcache.epoch <= epoch {
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log.Debug("Requiring new future ethash cache", "epoch", epoch+1)
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future = &cache{epoch: epoch + 1}
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- ethash.future = future
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+ ethash.fcache = future
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}
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}
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current.used = time.Now()
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@@ -254,7 +348,7 @@ func (ethash *Ethash) cache(block uint64) []uint32 {
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current.used = time.Now()
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current.lock.Unlock()
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- // If we exhusted the future cache, now's a goot time to regenerate it
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+ // If we exhausted the future cache, now's a good time to regenerate it
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if future != nil {
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go future.generate(ethash.cachedir, ethash.cachesondisk, ethash.tester)
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}
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@@ -264,7 +358,102 @@ func (ethash *Ethash) cache(block uint64) []uint32 {
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// Search implements PoW, attempting to find a nonce that satisfies the block's
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// difficulty requirements.
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func (ethash *Ethash) Search(block Block, stop <-chan struct{}) (uint64, []byte) {
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- return 0, nil
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+ // Extract some data from the block
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+ var (
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+ hash = block.HashNoNonce().Bytes()
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+ diff = block.Difficulty()
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+ target = new(big.Int).Div(maxUint256, diff)
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+ )
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+ // Retrieve the mining dataset
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+ dataset, size := ethash.dataset(block.NumberU64()), datasetSize(block.NumberU64())
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+
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+ // Start generating random nonces until we abort or find a good one
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+ var (
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+ attempts int64
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+
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+ rand = rand.New(rand.NewSource(time.Now().UnixNano()))
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+ nonce = uint64(rand.Int63())
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+ )
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+ for {
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+ select {
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+ case <-stop:
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+ // Mining terminated, update stats and abort
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+ ethash.hashrate.Mark(attempts)
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+ return 0, nil
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+
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+ default:
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+ // We don't have to update hash rate on every nonce, so update after after 2^X nonces
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+ attempts++
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+ if (attempts % (1 << 15)) == 0 {
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+ ethash.hashrate.Mark(attempts)
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+ attempts = 0
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+ }
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+ // Compute the PoW value of this nonce
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+ digest, result := hashimotoFull(size, dataset, hash, nonce)
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+ if new(big.Int).SetBytes(result).Cmp(target) <= 0 {
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+ return nonce, digest
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+ }
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+ nonce++
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+ }
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+ }
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+}
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+
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+// dataset tries to retrieve a mining dataset for the specified block number
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+// by first checking against a list of in-memory datasets, then against DAGs
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+// stored on disk, and finally generating one if none can be found.
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+func (ethash *Ethash) dataset(block uint64) []uint32 {
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+ epoch := block / epochLength
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+
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+ // If we have a PoW for that epoch, use that
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+ ethash.lock.Lock()
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+
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+ current, future := ethash.datasets[epoch], (*dataset)(nil)
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+ if current == nil {
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+ // No in-memory dataset, evict the oldest if the dataset limit was reached
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+ for len(ethash.datasets) >= ethash.dagsinmem {
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+ var evict *dataset
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+ for _, dataset := range ethash.datasets {
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+ if evict == nil || evict.used.After(dataset.used) {
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+ evict = dataset
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+ }
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+ }
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+ delete(ethash.datasets, evict.epoch)
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+
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+ log.Debug("Evicted ethash dataset", "epoch", evict.epoch, "used", evict.used)
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+ }
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+ // If we have the new cache pre-generated, use that, otherwise create a new one
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+ if ethash.fdataset != nil && ethash.fdataset.epoch == epoch {
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+ log.Debug("Using pre-generated dataset", "epoch", epoch)
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+ current = &dataset{epoch: ethash.fdataset.epoch} // Reload from disk
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+ ethash.fdataset = nil
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+ } else {
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+ log.Debug("Requiring new ethash dataset", "epoch", epoch)
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+ current = &dataset{epoch: epoch}
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+ }
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+ ethash.datasets[epoch] = current
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+
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+ // If we just used up the future dataset, or need a refresh, regenerate
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+ if ethash.fdataset == nil || ethash.fdataset.epoch <= epoch {
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+ log.Debug("Requiring new future ethash dataset", "epoch", epoch+1)
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+ future = &dataset{epoch: epoch + 1}
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+ ethash.fdataset = future
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+ }
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+ }
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+ current.used = time.Now()
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+ ethash.lock.Unlock()
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+
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+ // Wait for generation finish, bump the timestamp and finalize the cache
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+ current.generate(ethash.dagdir, ethash.dagsondisk, ethash.tester, false)
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+
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+ current.lock.Lock()
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+ current.used = time.Now()
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+ current.lock.Unlock()
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+
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+ // If we exhausted the future dataset, now's a good time to regenerate it
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+ if future != nil {
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+ go future.generate(ethash.dagdir, ethash.dagsondisk, ethash.tester, true) // Discard results from memorys
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+ }
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+ return current.dataset
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}
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// Hashrate implements PoW, returning the measured rate of the search invocations
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Péter Szilágyi