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// Copyright (c) 2009-2010 Satoshi Nakamoto
// Copyright (c) 2009-2017 The Bitcoin Core developers
// Distributed under the MIT software license, see the accompanying
// file COPYING or
#include <miner.h>
#include <amount.h>
#include <chain.h>
#include <chainparams.h>
#include <coins.h>
#include <consensus/consensus.h>
#include <consensus/tx_verify.h>
#include <consensus/merkle.h>
#include <consensus/validation.h>
#include <hash.h>
#include <validation.h>
#include <net.h>
#include <policy/feerate.h>
#include <policy/policy.h>
#include <pow.h>
#include <primitives/transaction.h>
#include <script/standard.h>
#include <timedata.h>
#include <util.h>
#include <utilmoneystr.h>
#include <validationinterface.h>
#include <algorithm>
#include <queue>
#include <utility>
// BitcoinMiner
// Unconfirmed transactions in the memory pool often depend on other
// transactions in the memory pool. When we select transactions from the
// pool, we select by highest fee rate of a transaction combined with all
// its ancestors.
uint64_t nLastBlockTx = 0;
uint64_t nLastBlockWeight = 0;
int64_t UpdateTime(CBlockHeader* pblock, const Consensus::Params& consensusParams, const CBlockIndex* pindexPrev)
int64_t nOldTime = pblock->nTime;
int64_t nNewTime = std::max(pindexPrev->GetMedianTimePast()+1, GetAdjustedTime());
if (nOldTime < nNewTime)
pblock->nTime = nNewTime;
// Updating time can change work required on testnet:
if (consensusParams.fPowAllowMinDifficultyBlocks)
pblock->nBits = GetNextWorkRequired(pindexPrev, pblock, consensusParams);
return nNewTime - nOldTime;
BlockAssembler::Options::Options() {
blockMinFeeRate = CFeeRate(DEFAULT_BLOCK_MIN_TX_FEE);
BlockAssembler::BlockAssembler(const CChainParams& params, const Options& options) : chainparams(params)
blockMinFeeRate = options.blockMinFeeRate;
// Limit weight to between 4K and MAX_BLOCK_WEIGHT-4K for sanity:
nBlockMaxWeight = std::max<size_t>(4000, std::min<size_t>(MAX_BLOCK_WEIGHT - 4000, options.nBlockMaxWeight));
static BlockAssembler::Options DefaultOptions(const CChainParams& params)
// Block resource limits
// If -blockmaxweight is not given, limit to DEFAULT_BLOCK_MAX_WEIGHT
BlockAssembler::Options options;
options.nBlockMaxWeight = gArgs.GetArg("-blockmaxweight", DEFAULT_BLOCK_MAX_WEIGHT);
if (gArgs.IsArgSet("-blockmintxfee")) {
CAmount n = 0;
ParseMoney(gArgs.GetArg("-blockmintxfee", ""), n);
options.blockMinFeeRate = CFeeRate(n);
} else {
options.blockMinFeeRate = CFeeRate(DEFAULT_BLOCK_MIN_TX_FEE);
return options;
BlockAssembler::BlockAssembler(const CChainParams& params) : BlockAssembler(params, DefaultOptions(params)) {}
void BlockAssembler::resetBlock()
// Reserve space for coinbase tx
nBlockWeight = 4000;
nBlockSigOpsCost = 400;
fIncludeWitness = false;
// These counters do not include coinbase tx
nBlockTx = 0;
nFees = 0;
std::unique_ptr<CBlockTemplate> BlockAssembler::CreateNewBlock(const CScript& scriptPubKeyIn, bool fMineWitnessTx)
int64_t nTimeStart = GetTimeMicros();
pblocktemplate.reset(new CBlockTemplate());
return nullptr;
pblock = &pblocktemplate->block; // pointer for convenience
// Add dummy coinbase tx as first transaction
pblocktemplate->vTxFees.push_back(-1); // updated at end
pblocktemplate->vTxSigOpsCost.push_back(-1); // updated at end
LOCK2(cs_main, mempool.cs);
CBlockIndex* pindexPrev = chainActive.Tip();
assert(pindexPrev != nullptr);
nHeight = pindexPrev->nHeight + 1;
pblock->nVersion = ComputeBlockVersion(pindexPrev, chainparams.GetConsensus());
// -regtest only: allow overriding block.nVersion with
// -blockversion=N to test forking scenarios
if (chainparams.MineBlocksOnDemand())
pblock->nVersion = gArgs.GetArg("-blockversion", pblock->nVersion);
pblock->nTime = GetAdjustedTime();
const int64_t nMedianTimePast = pindexPrev->GetMedianTimePast();
? nMedianTimePast
: pblock->GetBlockTime();
// Decide whether to include witness transactions
// This is only needed in case the witness softfork activation is reverted
// (which would require a very deep reorganization) or when
// -promiscuousmempoolflags is used.
// TODO: replace this with a call to main to assess validity of a mempool
// transaction (which in most cases can be a no-op).
fIncludeWitness = IsWitnessEnabled(pindexPrev, chainparams.GetConsensus()) && fMineWitnessTx;
int nPackagesSelected = 0;
int nDescendantsUpdated = 0;
addPackageTxs(nPackagesSelected, nDescendantsUpdated);
int64_t nTime1 = GetTimeMicros();
nLastBlockTx = nBlockTx;
nLastBlockWeight = nBlockWeight;
// Create coinbase transaction.
CMutableTransaction coinbaseTx;;[0].prevout.SetNull();
coinbaseTx.vout[0].scriptPubKey = scriptPubKeyIn;
coinbaseTx.vout[0].nValue = nFees + GetBlockSubsidy(nHeight, chainparams.GetConsensus());[0].scriptSig = CScript() << nHeight << OP_0;
pblock->vtx[0] = MakeTransactionRef(std::move(coinbaseTx));
pblocktemplate->vchCoinbaseCommitment = GenerateCoinbaseCommitment(*pblock, pindexPrev, chainparams.GetConsensus());
pblocktemplate->vTxFees[0] = -nFees;
LogPrintf("CreateNewBlock(): block weight: %u txs: %u fees: %ld sigops %d\n", GetBlockWeight(*pblock), nBlockTx, nFees, nBlockSigOpsCost);
// Fill in header
pblock->hashPrevBlock = pindexPrev->GetBlockHash();
UpdateTime(pblock, chainparams.GetConsensus(), pindexPrev);
pblock->nBits = GetNextWorkRequired(pindexPrev, pblock, chainparams.GetConsensus());
pblock->nNonce = 0;
pblocktemplate->vTxSigOpsCost[0] = WITNESS_SCALE_FACTOR * GetLegacySigOpCount(*pblock->vtx[0]);
CValidationState state;
if (!TestBlockValidity(state, chainparams, *pblock, pindexPrev, false, false)) {
throw std::runtime_error(strprintf("%s: TestBlockValidity failed: %s", __func__, FormatStateMessage(state)));
int64_t nTime2 = GetTimeMicros();
LogPrint(BCLog::BENCH, "CreateNewBlock() packages: %.2fms (%d packages, %d updated descendants), validity: %.2fms (total %.2fms)\n", 0.001 * (nTime1 - nTimeStart), nPackagesSelected, nDescendantsUpdated, 0.001 * (nTime2 - nTime1), 0.001 * (nTime2 - nTimeStart));
return std::move(pblocktemplate);
void BlockAssembler::onlyUnconfirmed(CTxMemPool::setEntries& testSet)
for (CTxMemPool::setEntries::iterator iit = testSet.begin(); iit != testSet.end(); ) {
// Only test txs not already in the block
if (inBlock.count(*iit)) {
else {
bool BlockAssembler::TestPackage(uint64_t packageSize, int64_t packageSigOpsCost) const
// TODO: switch to weight-based accounting for packages instead of vsize-based accounting.
if (nBlockWeight + WITNESS_SCALE_FACTOR * packageSize >= nBlockMaxWeight)
return false;
if (nBlockSigOpsCost + packageSigOpsCost >= MAX_BLOCK_SIGOPS_COST)
return false;
return true;
// Perform transaction-level checks before adding to block:
// - transaction finality (locktime)
// - premature witness (in case segwit transactions are added to mempool before
// segwit activation)
bool BlockAssembler::TestPackageTransactions(const CTxMemPool::setEntries& package)
for (const CTxMemPool::txiter it : package) {
if (!IsFinalTx(it->GetTx(), nHeight, nLockTimeCutoff))
return false;
if (!fIncludeWitness && it->GetTx().HasWitness())
return false;
return true;
void BlockAssembler::AddToBlock(CTxMemPool::txiter iter)
nBlockWeight += iter->GetTxWeight();
nBlockSigOpsCost += iter->GetSigOpCost();
nFees += iter->GetFee();
bool fPrintPriority = gArgs.GetBoolArg("-printpriority", DEFAULT_PRINTPRIORITY);
if (fPrintPriority) {
LogPrintf("fee %s txid %s\n",
CFeeRate(iter->GetModifiedFee(), iter->GetTxSize()).ToString(),
int BlockAssembler::UpdatePackagesForAdded(const CTxMemPool::setEntries& alreadyAdded,
indexed_modified_transaction_set &mapModifiedTx)
int nDescendantsUpdated = 0;
for (const CTxMemPool::txiter it : alreadyAdded) {
CTxMemPool::setEntries descendants;
mempool.CalculateDescendants(it, descendants);
// Insert all descendants (not yet in block) into the modified set
for (CTxMemPool::txiter desc : descendants) {
if (alreadyAdded.count(desc))
modtxiter mit = mapModifiedTx.find(desc);
if (mit == mapModifiedTx.end()) {
CTxMemPoolModifiedEntry modEntry(desc);
modEntry.nSizeWithAncestors -= it->GetTxSize();
modEntry.nModFeesWithAncestors -= it->GetModifiedFee();
modEntry.nSigOpCostWithAncestors -= it->GetSigOpCost();
} else {
mapModifiedTx.modify(mit, update_for_parent_inclusion(it));
return nDescendantsUpdated;
// Skip entries in mapTx that are already in a block or are present
// in mapModifiedTx (which implies that the mapTx ancestor state is
// stale due to ancestor inclusion in the block)
// Also skip transactions that we've already failed to add. This can happen if
// we consider a transaction in mapModifiedTx and it fails: we can then
// potentially consider it again while walking mapTx. It's currently
// guaranteed to fail again, but as a belt-and-suspenders check we put it in
// failedTx and avoid re-evaluation, since the re-evaluation would be using
// cached size/sigops/fee values that are not actually correct.
bool BlockAssembler::SkipMapTxEntry(CTxMemPool::txiter it, indexed_modified_transaction_set &mapModifiedTx, CTxMemPool::setEntries &failedTx)
assert (it != mempool.mapTx.end());
return mapModifiedTx.count(it) || inBlock.count(it) || failedTx.count(it);
void BlockAssembler::SortForBlock(const CTxMemPool::setEntries& package, CTxMemPool::txiter entry, std::vector<CTxMemPool::txiter>& sortedEntries)
// Sort package by ancestor count
// If a transaction A depends on transaction B, then A's ancestor count
// must be greater than B's. So this is sufficient to validly order the
// transactions for block inclusion.
sortedEntries.insert(sortedEntries.begin(), package.begin(), package.end());
std::sort(sortedEntries.begin(), sortedEntries.end(), CompareTxIterByAncestorCount());
// This transaction selection algorithm orders the mempool based
// on feerate of a transaction including all unconfirmed ancestors.
// Since we don't remove transactions from the mempool as we select them
// for block inclusion, we need an alternate method of updating the feerate
// of a transaction with its not-yet-selected ancestors as we go.
// This is accomplished by walking the in-mempool descendants of selected
// transactions and storing a temporary modified state in mapModifiedTxs.
// Each time through the loop, we compare the best transaction in
// mapModifiedTxs with the next transaction in the mempool to decide what
// transaction package to work on next.
void BlockAssembler::addPackageTxs(int &nPackagesSelected, int &nDescendantsUpdated)
// mapModifiedTx will store sorted packages after they are modified
// because some of their txs are already in the block
indexed_modified_transaction_set mapModifiedTx;
// Keep track of entries that failed inclusion, to avoid duplicate work
CTxMemPool::setEntries failedTx;
// Start by adding all descendants of previously added txs to mapModifiedTx
// and modifying them for their already included ancestors
UpdatePackagesForAdded(inBlock, mapModifiedTx);
CTxMemPool::indexed_transaction_set::index<ancestor_score>::type::iterator mi = mempool.mapTx.get<ancestor_score>().begin();
CTxMemPool::txiter iter;
// Limit the number of attempts to add transactions to the block when it is
// close to full; this is just a simple heuristic to finish quickly if the
// mempool has a lot of entries.
const int64_t MAX_CONSECUTIVE_FAILURES = 1000;
int64_t nConsecutiveFailed = 0;
while (mi != mempool.mapTx.get<ancestor_score>().end() || !mapModifiedTx.empty())
// First try to find a new transaction in mapTx to evaluate.
if (mi != mempool.mapTx.get<ancestor_score>().end() &&
SkipMapTxEntry(mempool.mapTx.project<0>(mi), mapModifiedTx, failedTx)) {
// Now that mi is not stale, determine which transaction to evaluate:
// the next entry from mapTx, or the best from mapModifiedTx?
bool fUsingModified = false;
modtxscoreiter modit = mapModifiedTx.get<ancestor_score>().begin();
if (mi == mempool.mapTx.get<ancestor_score>().end()) {
// We're out of entries in mapTx; use the entry from mapModifiedTx
iter = modit->iter;
fUsingModified = true;
} else {
// Try to compare the mapTx entry to the mapModifiedTx entry
iter = mempool.mapTx.project<0>(mi);
if (modit != mapModifiedTx.get<ancestor_score>().end() &&
CompareTxMemPoolEntryByAncestorFee()(*modit, CTxMemPoolModifiedEntry(iter))) {
// The best entry in mapModifiedTx has higher score
// than the one from mapTx.
// Switch which transaction (package) to consider
iter = modit->iter;
fUsingModified = true;
} else {
// Either no entry in mapModifiedTx, or it's worse than mapTx.
// Increment mi for the next loop iteration.
// We skip mapTx entries that are inBlock, and mapModifiedTx shouldn't
// contain anything that is inBlock.
uint64_t packageSize = iter->GetSizeWithAncestors();
CAmount packageFees = iter->GetModFeesWithAncestors();
int64_t packageSigOpsCost = iter->GetSigOpCostWithAncestors();
if (fUsingModified) {
packageSize = modit->nSizeWithAncestors;
packageFees = modit->nModFeesWithAncestors;
packageSigOpsCost = modit->nSigOpCostWithAncestors;
if (packageFees < blockMinFeeRate.GetFee(packageSize)) {
// Everything else we might consider has a lower fee rate
if (!TestPackage(packageSize, packageSigOpsCost)) {
if (fUsingModified) {
// Since we always look at the best entry in mapModifiedTx,
// we must erase failed entries so that we can consider the
// next best entry on the next loop iteration
if (nConsecutiveFailed > MAX_CONSECUTIVE_FAILURES && nBlockWeight >
nBlockMaxWeight - 4000) {
// Give up if we're close to full and haven't succeeded in a while
CTxMemPool::setEntries ancestors;
uint64_t nNoLimit = std::numeric_limits<uint64_t>::max();
std::string dummy;
mempool.CalculateMemPoolAncestors(*iter, ancestors, nNoLimit, nNoLimit, nNoLimit, nNoLimit, dummy, false);
// Test if all tx's are Final
if (!TestPackageTransactions(ancestors)) {
if (fUsingModified) {
// This transaction will make it in; reset the failed counter.
nConsecutiveFailed = 0;
// Package can be added. Sort the entries in a valid order.
std::vector<CTxMemPool::txiter> sortedEntries;
SortForBlock(ancestors, iter, sortedEntries);
for (size_t i=0; i<sortedEntries.size(); ++i) {
// Erase from the modified set, if present
// Update transactions that depend on each of these
nDescendantsUpdated += UpdatePackagesForAdded(ancestors, mapModifiedTx);
void IncrementExtraNonce(CBlock* pblock, const CBlockIndex* pindexPrev, unsigned int& nExtraNonce)
// Update nExtraNonce
static uint256 hashPrevBlock;
if (hashPrevBlock != pblock->hashPrevBlock)
nExtraNonce = 0;
hashPrevBlock = pblock->hashPrevBlock;
unsigned int nHeight = pindexPrev->nHeight+1; // Height first in coinbase required for block.version=2
CMutableTransaction txCoinbase(*pblock->vtx[0]);[0].scriptSig = (CScript() << nHeight << CScriptNum(nExtraNonce)) + COINBASE_FLAGS;
assert([0].scriptSig.size() <= 100);
pblock->vtx[0] = MakeTransactionRef(std::move(txCoinbase));
pblock->hashMerkleRoot = BlockMerkleRoot(*pblock);