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Make FindBlockByHeight constant-time.

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Remove the pnext pointer in CBlockIndex, and replace it with a
vBlockIndexByHeight vector (no effect on memory usage). pnext can
now be replaced by vBlockIndexByHeight[nHeight+1], but
FindBlockByHeight becomes constant-time.

This also means the entire mapBlockIndex structure and the block
index entries in it become purely blocktree-related data, and
independent from the currently active chain, potentially allowing
them to be protected by separate mutexes in the future.
This commit is contained in:
Pieter Wuille 2013-05-12 15:50:22 +02:00
parent 5b5d399593
commit 0fe8010a10
5 changed files with 36 additions and 51 deletions
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2
contrib/test-patches/bitcoind-comparison.patch
View file

@ -3,9 +3,9 @@ index 04a8618..519429a 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -31,8 +31,8 @@ CTxMemPool mempool;
unsigned int nTransactionsUpdated = 0;
map<uint256, CBlockIndex*> mapBlockIndex;
std::vector<CBlockIndex*> vBlockIndexByHeight;
-uint256 hashGenesisBlock("0x000000000019d6689c085ae165831e934ff763ae46a2a6c172b3f1b60a8ce26f");
-static CBigNum bnProofOfWorkLimit(~uint256(0) >> 32);
+uint256 hashGenesisBlock("0x0f9188f13cb7b2c71f2a335e3a4fc328bf5beb436012afca590b1a11466e2206");

54
src/main.cpp
View file

@ -31,6 +31,7 @@ CTxMemPool mempool;
unsigned int nTransactionsUpdated = 0;
map<uint256, CBlockIndex*> mapBlockIndex;
std::vector<CBlockIndex*> vBlockIndexByHeight;
uint256 hashGenesisBlock("0x000000000019d6689c085ae165831e934ff763ae46a2a6c172b3f1b60a8ce26f");
static CBigNum bnProofOfWorkLimit(~uint256(0) >> 32);
CBlockIndex* pindexGenesisBlock = NULL;
@ -1036,19 +1037,9 @@ bool GetTransaction(const uint256 &hash, CTransaction &txOut, uint256 &hashBlock
static CBlockIndex* pblockindexFBBHLast;
CBlockIndex* FindBlockByHeight(int nHeight)
{
CBlockIndex *pblockindex;
if (nHeight < nBestHeight / 2)
pblockindex = pindexGenesisBlock;
else
pblockindex = pindexBest;
if (pblockindexFBBHLast && abs(nHeight - pblockindex->nHeight) > abs(nHeight - pblockindexFBBHLast->nHeight))
pblockindex = pblockindexFBBHLast;
while (pblockindex->nHeight > nHeight)
pblockindex = pblockindex->pprev;
while (pblockindex->nHeight < nHeight)
pblockindex = pblockindex->pnext;
pblockindexFBBHLast = pblockindex;
return pblockindex;
if (nHeight >= (int)vBlockIndexByHeight.size())
return NULL;
return vBlockIndexByHeight[nHeight];
}
bool CBlock::ReadFromDisk(const CBlockIndex* pindex)
@ -1231,7 +1222,7 @@ void static InvalidBlockFound(CBlockIndex *pindex) {
pblocktree->WriteBlockIndex(CDiskBlockIndex(pindex));
setBlockIndexValid.erase(pindex);
InvalidChainFound(pindex);
if (pindex->pnext) {
if (pindex->GetNextInMainChain()) {
CValidationState stateDummy;
ConnectBestBlock(stateDummy); // reorganise away from the failed block
}
@ -1271,7 +1262,7 @@ bool ConnectBestBlock(CValidationState &state) {
if (pindexBest == NULL || pindexTest->nChainWork > pindexBest->nChainWork)
vAttach.push_back(pindexTest);
if (pindexTest->pprev == NULL || pindexTest->pnext != NULL) {
if (pindexTest->pprev == NULL || pindexTest->GetNextInMainChain()) {
reverse(vAttach.begin(), vAttach.end());
BOOST_FOREACH(CBlockIndex *pindexSwitch, vAttach) {
boost::this_thread::interruption_point();
@ -1849,15 +1840,10 @@ bool SetBestChain(CValidationState &state, CBlockIndex* pindexNew)
// At this point, all changes have been done to the database.
// Proceed by updating the memory structures.
// Disconnect shorter branch
BOOST_FOREACH(CBlockIndex* pindex, vDisconnect)
if (pindex->pprev)
pindex->pprev->pnext = NULL;
// Connect longer branch
// Register new best chain
vBlockIndexByHeight.resize(pindexNew->nHeight + 1);
BOOST_FOREACH(CBlockIndex* pindex, vConnect)
if (pindex->pprev)
pindex->pprev->pnext = pindex;
vBlockIndexByHeight[pindex->nHeight] = pindex;
// Resurrect memory transactions that were in the disconnected branch
BOOST_FOREACH(CTransaction& tx, vResurrect) {
@ -2609,12 +2595,12 @@ bool static LoadBlockIndexDB()
nBestHeight = pindexBest->nHeight;
nBestChainWork = pindexBest->nChainWork;
// set 'next' pointers in best chain
// register best chain
CBlockIndex *pindex = pindexBest;
while(pindex != NULL && pindex->pprev != NULL) {
CBlockIndex *pindexPrev = pindex->pprev;
pindexPrev->pnext = pindex;
pindex = pindexPrev;
vBlockIndexByHeight.resize(pindexBest->nHeight + 1);
while(pindex != NULL) {
vBlockIndexByHeight[pindex->nHeight] = pindex;
pindex = pindex->pprev;
}
printf("LoadBlockIndexDB(): hashBestChain=%s height=%d date=%s\n",
hashBestChain.ToString().c_str(), nBestHeight,
@ -2683,7 +2669,7 @@ bool VerifyDB() {
CBlockIndex *pindex = pindexState;
while (pindex != pindexBest) {
boost::this_thread::interruption_point();
pindex = pindex->pnext;
pindex = pindex->GetNextInMainChain();
CBlock block;
if (!block.ReadFromDisk(pindex))
return error("VerifyDB() : *** block.ReadFromDisk failed at %d, hash=%s", pindex->nHeight, pindex->GetBlockHash().ToString().c_str());
@ -2859,7 +2845,7 @@ void PrintBlockTree()
vector<CBlockIndex*>& vNext = mapNext[pindex];
for (unsigned int i = 0; i < vNext.size(); i++)
{
if (vNext[i]->pnext)
if (vNext[i]->GetNextInMainChain())
{
swap(vNext[0], vNext[i]);
break;
@ -3440,10 +3426,10 @@ bool static ProcessMessage(CNode* pfrom, string strCommand, CDataStream& vRecv)
// Send the rest of the chain
if (pindex)
pindex = pindex->pnext;
pindex = pindex->GetNextInMainChain();
int nLimit = 500;
printf("getblocks %d to %s limit %d\n", (pindex ? pindex->nHeight : -1), hashStop.ToString().c_str(), nLimit);
for (; pindex; pindex = pindex->pnext)
for (; pindex; pindex = pindex->GetNextInMainChain())
{
if (pindex->GetBlockHash() == hashStop)
{
@ -3483,14 +3469,14 @@ bool static ProcessMessage(CNode* pfrom, string strCommand, CDataStream& vRecv)
// Find the last block the caller has in the main chain
pindex = locator.GetBlockIndex();
if (pindex)
pindex = pindex->pnext;
pindex = pindex->GetNextInMainChain();
}
// we must use CBlocks, as CBlockHeaders won't include the 0x00 nTx count at the end
vector<CBlock> vHeaders;
int nLimit = 2000;
printf("getheaders %d to %s\n", (pindex ? pindex->nHeight : -1), hashStop.ToString().c_str());
for (; pindex; pindex = pindex->pnext)
for (; pindex; pindex = pindex->GetNextInMainChain())
{
vHeaders.push_back(pindex->GetBlockHeader());
if (--nLimit <= 0 || pindex->GetBlockHash() == hashStop)

24
src/main.h
View file

@ -69,6 +69,7 @@ extern CScript COINBASE_FLAGS;
extern CCriticalSection cs_main;
extern std::map<uint256, CBlockIndex*> mapBlockIndex;
extern std::vector<CBlockIndex*> vBlockIndexByHeight;
extern std::set<CBlockIndex*, CBlockIndexWorkComparator> setBlockIndexValid;
extern uint256 hashGenesisBlock;
extern CBlockIndex* pindexGenesisBlock;
@ -1589,10 +1590,8 @@ enum BlockStatus {
/** The block chain is a tree shaped structure starting with the
* genesis block at the root, with each block potentially having multiple
* candidates to be the next block. pprev and pnext link a path through the
* main/longest chain. A blockindex may have multiple pprev pointing back
* to it, but pnext will only point forward to the longest branch, or will
* be null if the block is not part of the longest chain.
* candidates to be the next block. A blockindex may have multiple pprev pointing
* to it, but at most one of them can be part of the currently active branch.
*/
class CBlockIndex
{
@ -1603,9 +1602,6 @@ public:
// pointer to the index of the predecessor of this block
CBlockIndex* pprev;
// (memory only) pointer to the index of the *active* successor of this block
CBlockIndex* pnext;
// height of the entry in the chain. The genesis block has height 0
int nHeight;
@ -1643,7 +1639,6 @@ public:
{
phashBlock = NULL;
pprev = NULL;
pnext = NULL;
nHeight = 0;
nFile = 0;
nDataPos = 0;
@ -1664,7 +1659,6 @@ public:
{
phashBlock = NULL;
pprev = NULL;
pnext = NULL;
nHeight = 0;
nFile = 0;
nDataPos = 0;
@ -1733,7 +1727,11 @@ public:
bool IsInMainChain() const
{
return (pnext || this == pindexBest);
return nHeight < (int)vBlockIndexByHeight.size() && vBlockIndexByHeight[nHeight] == this;
}
CBlockIndex *GetNextInMainChain() const {
return nHeight+1 >= (int)vBlockIndexByHeight.size() ? NULL : vBlockIndexByHeight[nHeight+1];
}
bool CheckIndex() const
@ -1762,9 +1760,9 @@ public:
const CBlockIndex* pindex = this;
for (int i = 0; i < nMedianTimeSpan/2; i++)
{
if (!pindex->pnext)
if (!pindex->GetNextInMainChain())
return GetBlockTime();
pindex = pindex->pnext;
pindex = pindex->GetNextInMainChain();
}
return pindex->GetMedianTimePast();
}
@ -1779,7 +1777,7 @@ public:
std::string ToString() const
{
return strprintf("CBlockIndex(pprev=%p, pnext=%p, nHeight=%d, merkle=%s, hashBlock=%s)",
pprev, pnext, nHeight,
pprev, GetNextInMainChain(), nHeight,
hashMerkleRoot.ToString().c_str(),
GetBlockHash().ToString().c_str());
}

5
src/rpcblockchain.cpp
View file

@ -65,8 +65,9 @@ Object blockToJSON(const CBlock& block, const CBlockIndex* blockindex)
if (blockindex->pprev)
result.push_back(Pair("previousblockhash", blockindex->pprev->GetBlockHash().GetHex()));
if (blockindex->pnext)
result.push_back(Pair("nextblockhash", blockindex->pnext->GetBlockHash().GetHex()));
CBlockIndex *pnext = blockindex->GetNextInMainChain();
if (pnext)
result.push_back(Pair("nextblockhash", pnext->GetBlockHash().GetHex()));
return result;
}

2
src/wallet.cpp
View file

@ -780,7 +780,7 @@ int CWallet::ScanForWalletTransactions(CBlockIndex* pindexStart, bool fUpdate)
if (AddToWalletIfInvolvingMe(tx.GetHash(), tx, &block, fUpdate))
ret++;
}
pindex = pindex->pnext;
pindex = pindex->GetNextInMainChain();
}
}
return ret;