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blockchain: update CalcBlockSubsidy.

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This betters CalcBlockSubsidy by allowing it to
calculate the requested block subsidy from a cached
subsidy entry regardless of its proximity to the
requested one.
This commit is contained in:
Donald Adu-Poku 2019-06-23 23:37:21 +00:00
parent 826d66bb56
commit 222e20680f
2 changed files with 43 additions and 12 deletions
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33
blockchain/subsidy.go
View File

@ -1,5 +1,5 @@
// Copyright (c) 2013-2015 The btcsuite developers
// Copyright (c) 2015-2018 The Decred developers
// Copyright (c) 2015-2019 The Decred developers
// Use of this source code is governed by an ISC
// license that can be found in the LICENSE file.
@ -85,15 +85,28 @@ func (s *SubsidyCache) CalcBlockSubsidy(height int64) int64 {
return cachedValue
}
// Is the previous one in the cache? If so, calculate
// the subsidy from the previous known value and store
// it in the database and the cache.
// If a cached block subsidy for the provided height is not found
// fetch the last cached block subsidy and generate the requested
// subsidy from that.
var lastCachedIter uint64
s.subsidyCacheLock.RLock()
cachedValue, existsInCache = s.subsidyCache[iteration-1]
for k := iteration - 1; k > 0; k-- {
cachedValue, existsInCache = s.subsidyCache[k]
if existsInCache {
lastCachedIter = k
break
}
}
s.subsidyCacheLock.RUnlock()
if existsInCache {
cachedValue *= s.params.MulSubsidy
cachedValue /= s.params.DivSubsidy
if lastCachedIter != 0 {
// Calculate the requested block subsidy using the last cached
// block subsidy.
diff := iteration - lastCachedIter
for i := uint64(0); i < diff; i++ {
cachedValue *= s.params.MulSubsidy
cachedValue /= s.params.DivSubsidy
}
s.subsidyCacheLock.Lock()
s.subsidyCache[iteration] = cachedValue
@ -102,9 +115,7 @@ func (s *SubsidyCache) CalcBlockSubsidy(height int64) int64 {
return cachedValue
}
// Calculate the subsidy from scratch and store in the
// cache. TODO If there's an older item in the cache,
// calculate it from that to save time.
// Calculate the subsidy from scratch and store in the cache.
subsidy := s.params.BaseSubsidy
for i := uint64(0); i < iteration; i++ {
subsidy *= s.params.MulSubsidy

22
blockchain/subsidy_test.go
View File

@ -1,5 +1,5 @@
// Copyright (c) 2013-2015 The btcsuite developers
// Copyright (c) 2015-2018 The Decred developers
// Copyright (c) 2015-2019 The Decred developers
// Use of this source code is governed by an ISC
// license that can be found in the LICENSE file.
@ -54,3 +54,23 @@ func TestBlockSubsidy(t *testing.T) {
t.Errorf("Bad total subsidy; want 2099999999800912, got %v", totalSubsidy)
}
}
func TestCachedCalcBlockSubsidy(t *testing.T) {
mainnet := &chaincfg.MainNetParams
cacheA := NewSubsidyCache(0, mainnet)
_ = cacheA.CalcBlockSubsidy(mainnet.SubsidyReductionInterval + 1)
// subsidyA is internally being calculated using the last cached subsidy.
subsidyA := cacheA.CalcBlockSubsidy((mainnet.SubsidyReductionInterval * 2) + 1)
cacheB := NewSubsidyCache(0, mainnet)
// subsidyB is internally being calculated from scratch.
subsidyB := cacheB.CalcBlockSubsidy((mainnet.SubsidyReductionInterval * 2) + 1)
if subsidyA != subsidyB {
t.Fatalf("Expected equal subsidies, got sudsidyA -> %v, "+
"subsidyB -> %v", subsidyA, subsidyB)
}
}