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Merge #7600: Mining: Select transactions using feerate-with-ancestors
29fac19 Add unit tests for ancestor feerate mining (Suhas Daftuar)
c82a4e9 Use ancestor-feerate based transaction selection for mining (Suhas Daftuar)
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sipa committed Jun 16, 2016
2 parents 9c3d0fa + 29fac19 commit 66db2d62d59817320c9182fc18e75a93b76828ea
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Showing 3 changed files with 432 additions and 1 deletion.
@@ -25,6 +25,7 @@
#include "utilmoneystr.h"
#include "validationinterface.h"

#include <algorithm>
#include <boost/thread.hpp>
#include <boost/tuple/tuple.hpp>
#include <queue>
@@ -134,7 +135,7 @@ CBlockTemplate* BlockAssembler::CreateNewBlock(const CScript& scriptPubKeyIn)
: pblock->GetBlockTime();


nLastBlockTx = nBlockTx;
nLastBlockSize = nBlockSize;
@@ -177,7 +178,38 @@ bool BlockAssembler::isStillDependent(CTxMemPool::txiter iter)
return false;

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, unsigned int packageSigOps)
if (nBlockSize + packageSize >= nBlockMaxSize)
return false;
if (nBlockSigOps + packageSigOps >= MAX_BLOCK_SIGOPS)
return false;
return true;

// Block size and sigops have already been tested. Check that all transactions
// are final.
bool BlockAssembler::TestPackageFinality(const CTxMemPool::setEntries& package)
BOOST_FOREACH (const CTxMemPool::txiter it, package) {
if (!IsFinalTx(it->GetTx(), nHeight, nLockTimeCutoff))
return false;
return true;

bool BlockAssembler::TestForBlock(CTxMemPool::txiter iter)
@@ -297,6 +329,178 @@ void BlockAssembler::addScoreTxs()

void BlockAssembler::UpdatePackagesForAdded(const CTxMemPool::setEntries& alreadyAdded,
indexed_modified_transaction_set &mapModifiedTx)
BOOST_FOREACH(const CTxMemPool::txiter it, alreadyAdded) {
CTxMemPool::setEntries descendants;
mempool.CalculateDescendants(it, descendants);
// Insert all descendants (not yet in block) into the modified set
BOOST_FOREACH(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.nSigOpCountWithAncestors -= it->GetSigOpCount();
} else {
mapModifiedTx.modify(mit, update_for_parent_inclusion(it));

// 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());
if (mapModifiedTx.count(it) || inBlock.count(it) || failedTx.count(it))
return true;
return false;

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()
// 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;
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() &&
CompareModifiedEntry()(*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();
unsigned int packageSigOps = iter->GetSigOpCountWithAncestors();
if (fUsingModified) {
packageSize = modit->nSizeWithAncestors;
packageFees = modit->nModFeesWithAncestors;
packageSigOps = modit->nSigOpCountWithAncestors;

if (packageFees < ::minRelayTxFee.GetFee(packageSize) && nBlockSize >= nBlockMinSize) {
// Everything else we might consider has a lower fee rate

if (!TestPackage(packageSize, packageSigOps)) {
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

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 (!TestPackageFinality(ancestors)) {
if (fUsingModified) {

// Package can be added. Sort the entries in a valid order.
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
UpdatePackagesForAdded(ancestors, mapModifiedTx);

void BlockAssembler::addPriorityTxs()
// How much of the block should be dedicated to high-priority transactions,
@@ -11,6 +11,8 @@

#include <stdint.h>
#include <memory>
#include "boost/multi_index_container.hpp"
#include "boost/multi_index/ordered_index.hpp"

class CBlockIndex;
class CChainParams;
@@ -29,6 +31,104 @@ struct CBlockTemplate
std::vector<int64_t> vTxSigOps;

// Container for tracking updates to ancestor feerate as we include (parent)
// transactions in a block
struct CTxMemPoolModifiedEntry {
CTxMemPoolModifiedEntry(CTxMemPool::txiter entry)
iter = entry;
nSizeWithAncestors = entry->GetSizeWithAncestors();
nModFeesWithAncestors = entry->GetModFeesWithAncestors();
nSigOpCountWithAncestors = entry->GetSigOpCountWithAncestors();

CTxMemPool::txiter iter;
uint64_t nSizeWithAncestors;
CAmount nModFeesWithAncestors;
unsigned int nSigOpCountWithAncestors;

/** Comparator for CTxMemPool::txiter objects.
* It simply compares the internal memory address of the CTxMemPoolEntry object
* pointed to. This means it has no meaning, and is only useful for using them
* as key in other indexes.
struct CompareCTxMemPoolIter {
bool operator()(const CTxMemPool::txiter& a, const CTxMemPool::txiter& b) const
return &(*a) < &(*b);

struct modifiedentry_iter {
typedef CTxMemPool::txiter result_type;
result_type operator() (const CTxMemPoolModifiedEntry &entry) const
return entry.iter;

// This matches the calculation in CompareTxMemPoolEntryByAncestorFee,
// except operating on CTxMemPoolModifiedEntry.
// TODO: refactor to avoid duplication of this logic.
struct CompareModifiedEntry {
bool operator()(const CTxMemPoolModifiedEntry &a, const CTxMemPoolModifiedEntry &b)
double f1 = (double)a.nModFeesWithAncestors * b.nSizeWithAncestors;
double f2 = (double)b.nModFeesWithAncestors * a.nSizeWithAncestors;
if (f1 == f2) {
return CTxMemPool::CompareIteratorByHash()(a.iter, b.iter);
return f1 > f2;

// A comparator that sorts transactions based on number of ancestors.
// This is sufficient to sort an ancestor package in an order that is valid
// to appear in a block.
struct CompareTxIterByAncestorCount {
bool operator()(const CTxMemPool::txiter &a, const CTxMemPool::txiter &b)
if (a->GetCountWithAncestors() != b->GetCountWithAncestors())
return a->GetCountWithAncestors() < b->GetCountWithAncestors();
return CTxMemPool::CompareIteratorByHash()(a, b);

typedef boost::multi_index_container<
// sorted by modified ancestor fee rate
// Reuse same tag from CTxMemPool's similar index
> indexed_modified_transaction_set;

typedef indexed_modified_transaction_set::nth_index<0>::type::iterator modtxiter;
typedef indexed_modified_transaction_set::index<ancestor_score>::type::iterator modtxscoreiter;

struct update_for_parent_inclusion
update_for_parent_inclusion(CTxMemPool::txiter it) : iter(it) {}

void operator() (CTxMemPoolModifiedEntry &e)
e.nModFeesWithAncestors -= iter->GetFee();
e.nSizeWithAncestors -= iter->GetTxSize();
e.nSigOpCountWithAncestors -= iter->GetSigOpCount();

CTxMemPool::txiter iter;

/** Generate a new block, without valid proof-of-work */
class BlockAssembler
@@ -74,12 +174,30 @@ class BlockAssembler
void addScoreTxs();
/** Add transactions based on tx "priority" */
void addPriorityTxs();
/** Add transactions based on feerate including unconfirmed ancestors */
void addPackageTxs();

// helper function for addScoreTxs and addPriorityTxs
/** Test if tx will still "fit" in the block */
bool TestForBlock(CTxMemPool::txiter iter);
/** Test if tx still has unconfirmed parents not yet in block */
bool isStillDependent(CTxMemPool::txiter iter);

// helper functions for addPackageTxs()
/** Remove confirmed (inBlock) entries from given set */
void onlyUnconfirmed(CTxMemPool::setEntries& testSet);
/** Test if a new package would "fit" in the block */
bool TestPackage(uint64_t packageSize, unsigned int packageSigOps);
/** Test if a set of transactions are all final */
bool TestPackageFinality(const CTxMemPool::setEntries& package);
/** Return true if given transaction from mapTx has already been evaluated,
* or if the transaction's cached data in mapTx is incorrect. */
bool SkipMapTxEntry(CTxMemPool::txiter it, indexed_modified_transaction_set &mapModifiedTx, CTxMemPool::setEntries &failedTx);
/** Sort the package in an order that is valid to appear in a block */
void SortForBlock(const CTxMemPool::setEntries& package, CTxMemPool::txiter entry, std::vector<CTxMemPool::txiter>& sortedEntries);
/** Add descendants of given transactions to mapModifiedTx with ancestor
* state updated assuming given transactions are inBlock. */
void UpdatePackagesForAdded(const CTxMemPool::setEntries& alreadyAdded, indexed_modified_transaction_set &mapModifiedTx);

/** Modify the extranonce in a block */

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