lbrycrd/src/miner.cpp

// Copyright (c) 2009-2010 Satoshi Nakamoto
// Copyright (c) 2009-2014 The Bitcoin Core developers
// Distributed under the MIT software license, see the accompanying
// file COPYING or http://www.opensource.org/licenses/mit-license.php.

#include "miner.h"

#include "amount.h"
#include "chain.h"
#include "chainparams.h"
#include "coins.h"
#include "consensus/consensus.h"
#include "consensus/validation.h"
#include "hash.h"
#include "main.h"
#include "nameclaim.h"
#include "claimtrie.h"
#include "net.h"
#include "policy/policy.h"
#include "pow.h"
#include "primitives/transaction.h"
#include "script/standard.h"
#include "timedata.h"
#include "txmempool.h"
#include "util.h"
#include "utilmoneystr.h"
#include "validationinterface.h"

#include <boost/thread.hpp>
#include <boost/tuple/tuple.hpp>

using namespace std;

//////////////////////////////////////////////////////////////////////////////
//
// 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 priority or fee rate, so we might consider
// transactions that depend on transactions that aren't yet in the block.
// The COrphan class keeps track of these 'temporary orphans' while
// CreateBlock is figuring out which transactions to include.
//
class COrphan
{
public:
    const CTransaction* ptx;
    set<uint256> setDependsOn;
    CFeeRate feeRate;
    double dPriority;

    COrphan(const CTransaction* ptxIn) : ptx(ptxIn), feeRate(0), dPriority(0)
    {
    }
};

uint64_t nLastBlockTx = 0;
uint64_t nLastBlockSize = 0;

// We want to sort transactions by priority and fee rate, so:
typedef boost::tuple<double, CFeeRate, const CTransaction*> TxPriority;
class TxPriorityCompare
{
    bool byFee;

public:
    TxPriorityCompare(bool _byFee) : byFee(_byFee) { }

    bool operator()(const TxPriority& a, const TxPriority& b)
    {
        if (byFee)
        {
            if (a.get<1>() == b.get<1>())
                return a.get<0>() < b.get<0>();
            return a.get<1>() < b.get<1>();
        }
        else
        {
            if (a.get<0>() == b.get<0>())
                return a.get<1>() < b.get<1>();
            return a.get<0>() < b.get<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;
}

CBlockTemplate* CreateNewBlock(const CScript& scriptPubKeyIn)
{
    const CChainParams& chainparams = Params();
    // Create new block
    auto_ptr<CBlockTemplate> pblocktemplate(new CBlockTemplate());
    if(!pblocktemplate.get())
        return NULL;
    CBlock *pblock = &pblocktemplate->block; // pointer for convenience

    // -regtest only: allow overriding block.nVersion with
    // -blockversion=N to test forking scenarios
    if (Params().MineBlocksOnDemand())
        pblock->nVersion = GetArg("-blockversion", pblock->nVersion);

    // Create coinbase tx
    CMutableTransaction txNew;
    txNew.vin.resize(1);
    txNew.vin[0].prevout.SetNull();
    txNew.vout.resize(1);
    txNew.vout[0].scriptPubKey = scriptPubKeyIn;

    // Add dummy coinbase tx as first transaction
    pblock->vtx.push_back(CTransaction());
    pblocktemplate->vTxFees.push_back(-1); // updated at end
    pblocktemplate->vTxSigOps.push_back(-1); // updated at end

    // Largest block you're willing to create:
    unsigned int nBlockMaxSize = GetArg("-blockmaxsize", DEFAULT_BLOCK_MAX_SIZE);
    // Limit to betweeen 1K and MAX_BLOCK_SIZE-1K for sanity:
    nBlockMaxSize = std::max((unsigned int)1000, std::min((unsigned int)(MAX_BLOCK_SIZE-1000), nBlockMaxSize));

    // How much of the block should be dedicated to high-priority transactions,
    // included regardless of the fees they pay
    unsigned int nBlockPrioritySize = GetArg("-blockprioritysize", DEFAULT_BLOCK_PRIORITY_SIZE);
    nBlockPrioritySize = std::min(nBlockMaxSize, nBlockPrioritySize);

    // Minimum block size you want to create; block will be filled with free transactions
    // until there are no more or the block reaches this size:
    unsigned int nBlockMinSize = GetArg("-blockminsize", DEFAULT_BLOCK_MIN_SIZE);
    nBlockMinSize = std::min(nBlockMaxSize, nBlockMinSize);

    // Collect memory pool transactions into the block
    CAmount nFees = 0;

    {
        LOCK2(cs_main, mempool.cs);
        CBlockIndex* pindexPrev = chainActive.Tip();
        const int nHeight = pindexPrev->nHeight + 1;
        pblock->nTime = GetAdjustedTime();
        CCoinsViewCache view(pcoinsTip);
        if (!pclaimTrie)
        {
            return NULL;
        }
        CClaimTrieCache trieCache(pclaimTrie);

        // Priority order to process transactions
        list<COrphan> vOrphan; // list memory doesn't move
        map<uint256, vector<COrphan*> > mapDependers;
        bool fPrintPriority = GetBoolArg("-printpriority", false);

        // This vector will be sorted into a priority queue:
        vector<TxPriority> vecPriority;
        vecPriority.reserve(mempool.mapTx.size());
        for (CTxMemPool::indexed_transaction_set::iterator mi = mempool.mapTx.begin();
             mi != mempool.mapTx.end(); ++mi)
        {
            const CTransaction& tx = mi->GetTx();
            if (tx.IsCoinBase() || !IsFinalTx(tx, nHeight, pblock->nTime))
                continue;

            COrphan* porphan = NULL;
            double dPriority = 0;
            CAmount nTotalIn = 0;
            bool fMissingInputs = false;
            BOOST_FOREACH(const CTxIn& txin, tx.vin)
            {
                // Read prev transaction
                if (!view.HaveCoins(txin.prevout.hash))
                {
                    // This should never happen; all transactions in the memory
                    // pool should connect to either transactions in the chain
                    // or other transactions in the memory pool.
                    if (!mempool.mapTx.count(txin.prevout.hash))
                    {
                        LogPrintf("ERROR: mempool transaction missing input\n");
                        if (fDebug) assert("mempool transaction missing input" == 0);
                        fMissingInputs = true;
                        if (porphan)
                            vOrphan.pop_back();
                        break;
                    }

                    // Has to wait for dependencies
                    if (!porphan)
                    {
                        // Use list for automatic deletion
                        vOrphan.push_back(COrphan(&tx));
                        porphan = &vOrphan.back();
                    }
                    mapDependers[txin.prevout.hash].push_back(porphan);
                    porphan->setDependsOn.insert(txin.prevout.hash);
                    nTotalIn += mempool.mapTx.find(txin.prevout.hash)->GetTx().vout[txin.prevout.n].nValue;
                    continue;
                }
                const CCoins* coins = view.AccessCoins(txin.prevout.hash);
                assert(coins);

                CAmount nValueIn = coins->vout[txin.prevout.n].nValue;
                nTotalIn += nValueIn;

                int nConf = nHeight - coins->nHeight;

                dPriority += (double)nValueIn * nConf;
            }
            if (fMissingInputs) continue;

            // Priority is sum(valuein * age) / modified_txsize
            unsigned int nTxSize = ::GetSerializeSize(tx, SER_NETWORK, PROTOCOL_VERSION);
            dPriority = tx.ComputePriority(dPriority, nTxSize);

            uint256 hash = tx.GetHash();
            mempool.ApplyDeltas(hash, dPriority, nTotalIn);

            CFeeRate feeRate(nTotalIn-tx.GetValueOut(), nTxSize);

            if (porphan)
            {
                porphan->dPriority = dPriority;
                porphan->feeRate = feeRate;
            }
            else
                vecPriority.push_back(TxPriority(dPriority, feeRate, &(mi->GetTx())));
        }

        // Collect transactions into block
        uint64_t nBlockSize = 1000;
        uint64_t nBlockTx = 0;
        int nBlockSigOps = 100;
        bool fSortedByFee = (nBlockPrioritySize <= 0);

        TxPriorityCompare comparer(fSortedByFee);
        std::make_heap(vecPriority.begin(), vecPriority.end(), comparer);

        while (!vecPriority.empty())
        {
            // Take highest priority transaction off the priority queue:
            double dPriority = vecPriority.front().get<0>();
            CFeeRate feeRate = vecPriority.front().get<1>();
            const CTransaction& tx = *(vecPriority.front().get<2>());

            std::pop_heap(vecPriority.begin(), vecPriority.end(), comparer);
            vecPriority.pop_back();

            // Size limits
            unsigned int nTxSize = ::GetSerializeSize(tx, SER_NETWORK, PROTOCOL_VERSION);
            if (nBlockSize + nTxSize >= nBlockMaxSize)
                continue;

            // Legacy limits on sigOps:
            unsigned int nTxSigOps = GetLegacySigOpCount(tx);
            if (nBlockSigOps + nTxSigOps >= MAX_BLOCK_SIGOPS)
                continue;

            // Skip free transactions if we're past the minimum block size:
            const uint256& hash = tx.GetHash();
            double dPriorityDelta = 0;
            CAmount nFeeDelta = 0;
            mempool.ApplyDeltas(hash, dPriorityDelta, nFeeDelta);
            if (fSortedByFee && (dPriorityDelta <= 0) && (nFeeDelta <= 0) && (feeRate < ::minRelayTxFee) && (nBlockSize + nTxSize >= nBlockMinSize))
                continue;

            // Prioritise by fee once past the priority size or we run out of high-priority
            // transactions:
            if (!fSortedByFee &&
                ((nBlockSize + nTxSize >= nBlockPrioritySize) || !AllowFree(dPriority)))
            {
                fSortedByFee = true;
                comparer = TxPriorityCompare(fSortedByFee);
                std::make_heap(vecPriority.begin(), vecPriority.end(), comparer);
            }

            if (!view.HaveInputs(tx))
                continue;

            CAmount nTxFees = view.GetValueIn(tx)-tx.GetValueOut();

            nTxSigOps += GetP2SHSigOpCount(tx, view);
            if (nBlockSigOps + nTxSigOps >= MAX_BLOCK_SIGOPS)
                continue;

            // Note that flags: we don't want to set mempool/IsStandard()
            // policy here, but we still have to ensure that the block we
            // create only contains transactions that are valid in new blocks.
            CValidationState state;
            if (!CheckInputs(tx, state, view, true, MANDATORY_SCRIPT_VERIFY_FLAGS, true))
                continue;

            typedef std::vector<std::pair<std::string, uint160> > spentClaimsType;
            spentClaimsType spentClaims;

            BOOST_FOREACH(const CTxIn& txin, tx.vin)
            {
                const CCoins* coins = view.AccessCoins(txin.prevout.hash);
                // This seems to happen during testing, and should never happen otherwise
                if (!coins || txin.prevout.n >= coins->vout.size())
                {
                    LogPrintf("%s: !coins || txin.prevout.n >= coins->vout.size(). txin.prevout.hash = %s\n", __func__, txin.prevout.hash.GetHex());
                    if (coins)
                        LogPrintf("coins is not null. txin.prevout.n = %d, coins->vout.size() = %d\n", txin.prevout.n, coins->vout.size());
                    continue;
                }

                std::vector<std::vector<unsigned char> > vvchParams;
                int op;

                if (DecodeClaimScript(coins->vout[txin.prevout.n].scriptPubKey, op, vvchParams))
                {
                    if (op == OP_CLAIM_NAME || op == OP_UPDATE_CLAIM)
                    {
                        uint160 claimId;
                        if (op == OP_CLAIM_NAME)
                        {
                            assert(vvchParams.size() == 2);
                            claimId = ClaimIdHash(txin.prevout.hash, txin.prevout.n);
                        }
                        else if (op == OP_UPDATE_CLAIM)
                        {
                            assert(vvchParams.size() == 3);
                            claimId = uint160(vvchParams[1]);
                        }
                        std::string name(vvchParams[0].begin(), vvchParams[0].end());
                        int throwaway;
                        if (trieCache.spendClaim(name, txin.prevout.hash, txin.prevout.n, coins->nHeight, throwaway))
                        {
                            std::pair<std::string, uint160> entry(name, claimId);
                            spentClaims.push_back(entry);
                        }
                        else
                        {
                            LogPrintf("%s(): The claim was not found in the trie or queue and therefore can't be updated\n", __func__);
                        }
                    }
                    else if (op == OP_SUPPORT_CLAIM)
                    {
                        assert(vvchParams.size() == 2);
                        std::string name(vvchParams[0].begin(), vvchParams[0].end());
                        int throwaway;
                        if (!trieCache.spendSupport(name, txin.prevout.hash, txin.prevout.n, coins->nHeight, throwaway))
                        {
                            LogPrintf("%s(): The support was not found in the trie or queue\n", __func__);
                        }
                    }
                }
            }
            
            UpdateCoins(tx, state, view, nHeight);
            
            for (unsigned int i = 0; i < tx.vout.size(); ++i)
            {
                const CTxOut& txout = tx.vout[i];
            
                std::vector<std::vector<unsigned char> > vvchParams;
                int op;
                if (DecodeClaimScript(txout.scriptPubKey, op, vvchParams))
                {
                    if (op == OP_CLAIM_NAME)
                    {
                        assert(vvchParams.size() == 2);
                        std::string name(vvchParams[0].begin(), vvchParams[0].end());
                        if (!trieCache.addClaim(name, tx.GetHash(), i, ClaimIdHash(tx.GetHash(), i), txout.nValue, nHeight))
                        {
                            LogPrintf("%s: Something went wrong inserting the name\n", __func__);
                        }
                    }
                    else if (op == OP_UPDATE_CLAIM)
                    {
                        assert(vvchParams.size() == 3);
                        std::string name(vvchParams[0].begin(), vvchParams[0].end());
                        uint160 claimId(vvchParams[1]);
                        spentClaimsType::iterator itSpent;
                        for (itSpent = spentClaims.begin(); itSpent != spentClaims.end(); ++itSpent)
                        {
                            if (itSpent->first == name && itSpent->second == claimId)
                            {
                                break;
                            }
                        }
                        if (itSpent != spentClaims.end())
                        {
                            spentClaims.erase(itSpent);
                            if (!trieCache.addClaim(name, tx.GetHash(), i, claimId, txout.nValue, nHeight))
                            {
                                LogPrintf("%s: Something went wrong updating a claim\n", __func__);
                            }
                        }
                        else
                        {
                            LogPrintf("%s(): This update refers to a claim that was not found in the trie or queue, and therefore cannot be updated. The claim may have expired or it may have never existed.\n", __func__);
                        }
                    }
                    else if (op == OP_SUPPORT_CLAIM)
                    {
                        assert(vvchParams.size() == 2);
                        std::string name(vvchParams[0].begin(), vvchParams[0].end());
                        uint160 supportedClaimId(vvchParams[1]);
                        if (!trieCache.addSupport(name, tx.GetHash(), i, txout.nValue, supportedClaimId, nHeight))
                        {
                            LogPrintf("%s: Something went wrong inserting the claim support\n", __func__);
                        }
                    }
                }
            }

            // Added
            pblock->vtx.push_back(tx);
            pblocktemplate->vTxFees.push_back(nTxFees);
            pblocktemplate->vTxSigOps.push_back(nTxSigOps);
            nBlockSize += nTxSize;
            ++nBlockTx;
            nBlockSigOps += nTxSigOps;
            nFees += nTxFees;

            if (fPrintPriority)
            {
                LogPrintf("priority %.1f fee %s txid %s\n",
                    dPriority, feeRate.ToString(), tx.GetHash().ToString());
            }

            // Add transactions that depend on this one to the priority queue
            if (mapDependers.count(hash))
            {
                BOOST_FOREACH(COrphan* porphan, mapDependers[hash])
                {
                    if (!porphan->setDependsOn.empty())
                    {
                        porphan->setDependsOn.erase(hash);
                        if (porphan->setDependsOn.empty())
                        {
                            vecPriority.push_back(TxPriority(porphan->dPriority, porphan->feeRate, porphan->ptx));
                            std::push_heap(vecPriority.begin(), vecPriority.end(), comparer);
                        }
                    }
                }
            }
        }

        nLastBlockTx = nBlockTx;
        nLastBlockSize = nBlockSize;
        LogPrintf("CreateNewBlock(): total size %u\n", nBlockSize);

        // Compute final coinbase transaction.
        txNew.vout[0].nValue = nFees + GetBlockSubsidy(nHeight, chainparams.GetConsensus());
        txNew.vin[0].scriptSig = CScript() << nHeight << OP_0;
        pblock->vtx[0] = txNew;
        pblocktemplate->vTxFees[0] = -nFees;

        // Fill in header
        pblock->hashPrevBlock  = pindexPrev->GetBlockHash();
        UpdateTime(pblock, Params().GetConsensus(), pindexPrev);
        pblock->nBits          = GetNextWorkRequired(pindexPrev, pblock, Params().GetConsensus());
        pblock->nNonce         = 0;
        pblocktemplate->vTxSigOps[0] = GetLegacySigOpCount(pblock->vtx[0]);
        claimQueueRowType dummyInsertUndo;
        claimQueueRowType dummyExpireUndo;
        supportQueueRowType dummyInsertSupportUndo;
        std::vector<std::pair<std::string, int> > dummyTakeoverHeightUndo;
        trieCache.incrementBlock(dummyInsertUndo, dummyExpireUndo, dummyInsertSupportUndo, dummyTakeoverHeightUndo);
        pblock->hashClaimTrie = trieCache.getMerkleHash();

        CValidationState state;
        if (!TestBlockValidity(state, *pblock, pindexPrev, false, false))
            throw std::runtime_error("CreateNewBlock(): TestBlockValidity failed");
    }

    return pblocktemplate.release();
}

void IncrementExtraNonce(CBlock* pblock, const CBlockIndex* pindexPrev, unsigned int& nExtraNonce)
{
    // Update nExtraNonce
    static uint256 hashPrevBlock;
    if (hashPrevBlock != pblock->hashPrevBlock)
    {
        nExtraNonce = 0;
        hashPrevBlock = pblock->hashPrevBlock;
    }
    ++nExtraNonce;
    unsigned int nHeight = pindexPrev->nHeight+1; // Height first in coinbase required for block.version=2
    CMutableTransaction txCoinbase(pblock->vtx[0]);
    txCoinbase.vin[0].scriptSig = (CScript() << nHeight << CScriptNum(nExtraNonce)) + COINBASE_FLAGS;
    assert(txCoinbase.vin[0].scriptSig.size() <= 100);

    pblock->vtx[0] = txCoinbase;
    pblock->hashMerkleRoot = pblock->ComputeMerkleRoot();
}

//////////////////////////////////////////////////////////////////////////////
//
// Internal miner
//

//
// ScanHash scans nonces looking for a hash with at least some zero bits.
// The nonce is usually preserved between calls, but periodically or if the
// nonce is 0xffff0000 or above, the block is rebuilt and nNonce starts over at
// zero.
//
bool static ScanHash(const CBlockHeader *pblock, uint32_t& nNonce, uint256 *phash)
{
    // Write the first 108 bytes of the block header to a double-SHA256 state.
    CHash256 hasher;
    CDataStream ss(SER_NETWORK, PROTOCOL_VERSION);
    ss << *pblock;
    assert(ss.size() == 112);
    hasher.Write((unsigned char*)&ss[0], 108);

    while (true) {
        nNonce++;

        // Write the last 4 bytes of the block header (the nonce) to a copy of
        // the double-SHA256 state, and compute the result.
        CHash256(hasher).Write((unsigned char*)&nNonce, 4).Finalize((unsigned char*)phash);

        // Return the nonce if the hash has at least some zero bits,
        // caller will check if it has enough to reach the target
        if (((uint16_t*)phash)[15] == 0)
            return true;

        // If nothing found after trying for a while, return -1
        if ((nNonce & 0xfff) == 0)
            return false;
    }
}

static bool ProcessBlockFound(const CBlock* pblock, const CChainParams& chainparams)
{
    LogPrintf("%s\n", pblock->ToString());
    LogPrintf("generated %s\n", FormatMoney(pblock->vtx[0].vout[0].nValue));

    // Found a solution
    {
        LOCK(cs_main);
        if (pblock->hashPrevBlock != chainActive.Tip()->GetBlockHash())
            return error("BitcoinMiner: generated block is stale");
    }

    // Inform about the new block
    GetMainSignals().BlockFound(pblock->GetHash());

    // Process this block the same as if we had received it from another node
    CValidationState state;
    if (!ProcessNewBlock(state, NULL, pblock, true, NULL))
        return error("BitcoinMiner: ProcessNewBlock, block not accepted");

    return true;
}

void static BitcoinMiner(const CChainParams& chainparams)
{
    LogPrintf("BitcoinMiner started\n");
    SetThreadPriority(THREAD_PRIORITY_LOWEST);
    RenameThread("bitcoin-miner");

    unsigned int nExtraNonce = 0;

    boost::shared_ptr<CReserveScript> coinbaseScript;
    GetMainSignals().ScriptForMining(coinbaseScript);

    try {
        // Throw an error if no script was provided.  This can happen
        // due to some internal error but also if the keypool is empty.
        // In the latter case, already the pointer is NULL.
        if (!coinbaseScript || coinbaseScript->reserveScript.empty())
            throw std::runtime_error("No coinbase script available (mining requires a wallet)");

        while (true) {
            if (chainparams.MiningRequiresPeers()) {
                // Busy-wait for the network to come online so we don't waste time mining
                // on an obsolete chain. In regtest mode we expect to fly solo.
                do {
                    bool fvNodesEmpty;
                    {
                        LOCK(cs_vNodes);
                        fvNodesEmpty = vNodes.empty();
                    }
                    if (!fvNodesEmpty && !IsInitialBlockDownload())
                        break;
                    MilliSleep(1000);
                } while (true);
            }

            //
            // Create new block
            //
            unsigned int nTransactionsUpdatedLast = mempool.GetTransactionsUpdated();
            CBlockIndex* pindexPrev = chainActive.Tip();

            auto_ptr<CBlockTemplate> pblocktemplate(CreateNewBlock(coinbaseScript->reserveScript));
            if (!pblocktemplate.get())
            {
                LogPrintf("Error in BitcoinMiner: Keypool ran out, please call keypoolrefill before restarting the mining thread\n");
                return;
            }
            CBlock *pblock = &pblocktemplate->block;
            IncrementExtraNonce(pblock, pindexPrev, nExtraNonce);

            LogPrintf("Running BitcoinMiner with %u transactions in block (%u bytes)\n", pblock->vtx.size(),
                ::GetSerializeSize(*pblock, SER_NETWORK, PROTOCOL_VERSION));

            //
            // Search
            //
            int64_t nStart = GetTime();
            arith_uint256 hashTarget = arith_uint256().SetCompact(pblock->nBits);
            uint256 hash;
            uint32_t nNonce = 0;
            while (true) {
                // Check if something found
                if (ScanHash(pblock, nNonce, &hash))
                {
                    if (UintToArith256(hash) <= hashTarget)
                    {
                        // Found a solution
                        pblock->nNonce = nNonce;
                        assert(hash == pblock->GetHash());

                        SetThreadPriority(THREAD_PRIORITY_NORMAL);
                        LogPrintf("BitcoinMiner:\n");
                        LogPrintf("proof-of-work found  \n  hash: %s  \ntarget: %s\n", hash.GetHex(), hashTarget.GetHex());
                        ProcessBlockFound(pblock, chainparams);
                        SetThreadPriority(THREAD_PRIORITY_LOWEST);
                        coinbaseScript->KeepScript();

                        // In regression test mode, stop mining after a block is found.
                        if (chainparams.MineBlocksOnDemand())
                            throw boost::thread_interrupted();

                        break;
                    }
                }

                // Check for stop or if block needs to be rebuilt
                boost::this_thread::interruption_point();
                // Regtest mode doesn't require peers
                if (vNodes.empty() && chainparams.MiningRequiresPeers())
                    break;
                if (nNonce >= 0xffff0000)
                    break;
                if (mempool.GetTransactionsUpdated() != nTransactionsUpdatedLast && GetTime() - nStart > 60)
                    break;
                if (pindexPrev != chainActive.Tip())
                    break;

                // Update nTime every few seconds
                if (UpdateTime(pblock, chainparams.GetConsensus(), pindexPrev) < 0)
                    break; // Recreate the block if the clock has run backwards,
                           // so that we can use the correct time.
                if (chainparams.GetConsensus().fPowAllowMinDifficultyBlocks)
                {
                    // Changing pblock->nTime can change work required on testnet:
                    hashTarget.SetCompact(pblock->nBits);
                }
            }
        }
    }
    catch (const boost::thread_interrupted&)
    {
        LogPrintf("BitcoinMiner terminated\n");
        throw;
    }
    catch (const std::runtime_error &e)
    {
        LogPrintf("BitcoinMiner runtime error: %s\n", e.what());
        return;
    }
}

void GenerateBitcoins(bool fGenerate, int nThreads, const CChainParams& chainparams)
{
    static boost::thread_group* minerThreads = NULL;

    if (nThreads < 0)
        nThreads = GetNumCores();

    if (minerThreads != NULL)
    {
        minerThreads->interrupt_all();
        delete minerThreads;
        minerThreads = NULL;
    }

    if (nThreads == 0 || !fGenerate)
        return;

    minerThreads = new boost::thread_group();
    for (int i = 0; i < nThreads; i++)
        minerThreads->create_thread(boost::bind(&BitcoinMiner, boost::cref(chainparams)));
}