text: // Copyright (c) 2009-2010 Satoshi Nakamoto
  // Copyright (c) 2009-2014 The Bitcoin developers
  // Copyright (c) 2014-2015 The Dash developers
  // Copyright (c) 2015-2017 The PIVX developers
  // Copyright (c) 2017-2020 The Khrysus developers
  // Distributed under the MIT/X11 software license, see the accompanying
  // file COPYING or http://www.opensource.org/licenses/mit-license.php.
  
  #include "miner.h"
  
  #include "amount.h"
  #include "hash.h"
  #include "main.h"
  #include "masternode-sync.h"
  #include "net.h"
  #include "pow.h"
  #include "primitives/block.h"
  #include "primitives/transaction.h"
  #include "timedata.h"
  #include "util.h"
  #include "utilmoneystr.h"
  #ifdef ENABLE_WALLET
  #include "wallet.h"
  #endif
  #include "masternode-payments.h"
  #include "spork.h"
  
  #include <boost/thread.hpp>
  #include <boost/tuple/tuple.hpp>
  
  using namespace std;
  
  //////////////////////////////////////////////////////////////////////////////
  //
  // KhrysusMiner
  //
  
  //
  // 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;
  int64_t nLastCoinStakeSearchInterval = 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>();
          }
      }
  };
  
  void UpdateTime(CBlockHeader* pblock, const CBlockIndex* pindexPrev)
  {
      pblock->nTime = std::max(pindexPrev->GetMedianTimePast() + 1, GetAdjustedTime());
  
      // Updating time can change work required on testnet:
      if (Params().AllowMinDifficultyBlocks())
          pblock->nBits = GetNextWorkRequired(pindexPrev, pblock);
  }
  
  CBlockTemplate* CreateNewBlock(const CScript& scriptPubKeyIn, CWallet* pwallet, bool fProofOfStake)
  {
      CReserveKey reservekey(pwallet);
  
      // Create new block
      unique_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);
  
      pblock->nVersion = 4;
  
      // Create coinbase tx
      CMutableTransaction txNew;
      txNew.vin.resize(1);
      txNew.vin[0].prevout.SetNull();
      txNew.vout.resize(1);
      txNew.vout[0].scriptPubKey = scriptPubKeyIn;
  
      CBlockIndex* prev = chainActive.Tip();
      txNew.vout[0].nValue = GetBlockValue(prev->nHeight);
  
      pblock->vtx.push_back(txNew);
      pblocktemplate->vTxFees.push_back(-1);   // updated at end
      pblocktemplate->vTxSigOps.push_back(-1); // updated at end
  
      // ppcoin: if coinstake available add coinstake tx
      static int64_t nLastCoinStakeSearchTime = GetAdjustedTime(); // only initialized at startup
  
      if (fProofOfStake) {
          boost::this_thread::interruption_point();
          pblock->nTime = GetAdjustedTime();
          CBlockIndex* pindexPrev = chainActive.Tip();
          pblock->nBits = GetNextWorkRequired(pindexPrev, pblock);
          CMutableTransaction txCoinStake;
          int64_t nSearchTime = pblock->nTime; // search to current time
          bool fStakeFound = false;
          if (nSearchTime >= nLastCoinStakeSearchTime) {
              unsigned int nTxNewTime = 0;
              if (pwallet->CreateCoinStake(*pwallet, pblock->nBits, nSearchTime - nLastCoinStakeSearchTime, txCoinStake, nTxNewTime)) {
                  pblock->nTime = nTxNewTime;
                  pblock->vtx[0].vout[0].SetEmpty();
                  pblock->vtx.push_back(CTransaction(txCoinStake));
                  fStakeFound = true;
              }
              nLastCoinStakeSearchInterval = nSearchTime - nLastCoinStakeSearchTime;
              nLastCoinStakeSearchTime = nSearchTime;
          }
  
          if (!fStakeFound)
              return NULL;
      }
  
      // 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;
          CCoinsViewCache view(pcoinsTip);
  
          // 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 (map<uint256, CTxMemPoolEntry>::iterator mi = mempool.mapTx.begin();
               mi != mempool.mapTx.end(); ++mi) {
              const CTransaction& tx = mi->second.GetTx();
              if (tx.IsCoinBase() || tx.IsCoinStake() || !IsFinalTx(tx, nHeight))
                  continue;
  
              COrphan* porphan = NULL;
              double dPriority = 0;
              CAmount nTotalIn = 0;
              bool fMissingInputs = false;
              for (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[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->second.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);
  
          vector<CBigNum> vBlockSerials;
          vector<CBigNum> vTxSerials;
          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 nMaxBlockSigOps = MAX_BLOCK_SIGOPS;
              unsigned int nTxSigOps = GetLegacySigOpCount(tx);
              if (nBlockSigOps + nTxSigOps >= nMaxBlockSigOps)
                  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 >= nMaxBlockSigOps)
                  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;
  
              CTxUndo txundo;
              UpdateCoins(tx, state, view, txundo, nHeight);
  
              // Added
              pblock->vtx.push_back(tx);
              pblocktemplate->vTxFees.push_back(nTxFees);
              pblocktemplate->vTxSigOps.push_back(nTxSigOps);
              nBlockSize += nTxSize;
              ++nBlockTx;
              nBlockSigOps += nTxSigOps;
              nFees += nTxFees;
  
              for (const CBigNum bnSerial : vTxSerials)
                  vBlockSerials.emplace_back(bnSerial);
  
              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);
                          }
                      }
                  }
              }
          }
  
          if (!fProofOfStake) {
              //Masternode and general budget payments
              FillBlockPayee(txNew, nFees, fProofOfStake);
  
              //Make payee
              if (txNew.vout.size() > 1) {
                  pblock->payee = txNew.vout[1].scriptPubKey;
              }
          }
  
          nLastBlockTx = nBlockTx;
          nLastBlockSize = nBlockSize;
          LogPrintf("CreateNewBlock(): total size %u\n", nBlockSize);
  
          // Compute final coinbase transaction.
          pblock->vtx[0].vin[0].scriptSig = CScript() << nHeight << OP_0;
          if (!fProofOfStake) {
              pblock->vtx[0] = txNew;
              pblocktemplate->vTxFees[0] = -nFees;
          }
  
          // Fill in header
          pblock->hashPrevBlock = pindexPrev->GetBlockHash();
          if (!fProofOfStake)
              UpdateTime(pblock, pindexPrev);
          pblock->nBits = GetNextWorkRequired(pindexPrev, pblock);
          pblock->nNonce = 0;
          pblocktemplate->vTxSigOps[0] = GetLegacySigOpCount(pblock->vtx[0]);
  
          // CValidationState state;
          // if (!TestBlockValidity(state, *pblock, pindexPrev, false, false)) {
          //     LogPrintf("CreateNewBlock() : TestBlockValidity failed\n");
          //     mempool.clear();
          //     return NULL;
          // }
      }
  
      return pblocktemplate.release();
  }
  
  void IncrementExtraNonce(CBlock* pblock, 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->BuildMerkleTree();
  }
  
  #ifdef ENABLE_WALLET
  //////////////////////////////////////////////////////////////////////////////
  //
  // Internal miner
  //
  double dHashesPerSec = 0.0;
  int64_t nHPSTimerStart = 0;
  
  CBlockTemplate* CreateNewBlockWithKey(CReserveKey& reservekey, CWallet* pwallet, bool fProofOfStake)
  {
      CPubKey pubkey;
      if (!reservekey.GetReservedKey(pubkey))
          return NULL;
  
      CScript scriptPubKey = CScript() << ToByteVector(pubkey) << OP_CHECKSIG;
      return CreateNewBlock(scriptPubKey, pwallet, fProofOfStake);
  }
  
  bool ProcessBlockFound(CBlock* pblock, CWallet& wallet, CReserveKey& reservekey)
  {
      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("KhrysusMiner : generated block is stale");
      }
  
      // Remove key from key pool
      reservekey.KeepKey();
  
      // Track how many getdata requests this block gets
      {
          LOCK(wallet.cs_wallet);
          wallet.mapRequestCount[pblock->GetHash()] = 0;
      }
  
      // Process this block the same as if we had received it from another node
      CValidationState state;
      if (!ProcessNewBlock(state, NULL, pblock))
          return error("KhrysusMiner : ProcessNewBlock, block not accepted");
  
      for (CNode* node : vNodes) {
          node->PushInventory(CInv(MSG_BLOCK, pblock->GetHash()));
      }
  
      return true;
  }
  
  bool fGenerateBitcoins = false;
  
  // ***TODO*** that part changed in bitcoin, we are using a mix with old one here for now
  
  void BitcoinMiner(CWallet* pwallet, bool fProofOfStake)
  {
      LogPrintf("KhrysusMiner started\n");
      SetThreadPriority(THREAD_PRIORITY_LOWEST);
      RenameThread("khrysus-miner");
  
      // Each thread has its own key and counter
      CReserveKey reservekey(pwallet);
      unsigned int nExtraNonce = 0;
  
      //control the amount of times the client will check for mintable coins
      static bool fMintableCoins = false;
      static int nMintableLastCheck = 0;
  
      while (fGenerateBitcoins || fProofOfStake) {
          if (fProofOfStake && (GetTime() - nMintableLastCheck > 5 * 60)) // 5 minute check time
          {
              nMintableLastCheck = GetTime();
              fMintableCoins = pwallet->MintableCoins();
          }
  
          if (fProofOfStake) {
              if (chainActive.Tip()->nHeight < Params().LAST_POW_BLOCK()) {
                  MilliSleep(5000);
                  continue;
              }
  
              if (chainActive.Tip()->nTime < Params().GenesisBlock().nTime || vNodes.empty() || pwallet->IsLocked() || !fMintableCoins || nReserveBalance >= pwallet->GetBalance()) {
                  nLastCoinStakeSearchInterval = 0;
                  MilliSleep(30000);
                  continue;
              }
  
              if (mapHashedBlocks.count(chainActive.Tip()->nHeight)) //search our map of hashed blocks, see if bestblock has been hashed yet
              {
                  if (GetTime() - mapHashedBlocks[chainActive.Tip()->nHeight] < max(pwallet->nHashInterval, (unsigned int)1)) // wait half of the nHashDrift with max wait of 3 minutes
                  {
                      MilliSleep(30000);
                      continue;
                  }
              }
          }
  
          //
          // Create new block
          //
          unsigned int nTransactionsUpdatedLast = mempool.GetTransactionsUpdated();
          CBlockIndex* pindexPrev = chainActive.Tip();
          if (!pindexPrev)
              continue;
  
          unique_ptr<CBlockTemplate> pblocktemplate(CreateNewBlockWithKey(reservekey, pwallet, fProofOfStake));
          if (!pblocktemplate.get())
              continue;
  
          CBlock* pblock = &pblocktemplate->block;
          IncrementExtraNonce(pblock, pindexPrev, nExtraNonce);
  
          //Stake miner main
          if (fProofOfStake) {
              LogPrintf("CPUMiner : proof-of-stake block found %s \n", pblock->GetHash().ToString().c_str());
  
              if (!pblock->SignBlock(*pwallet)) {
                  LogPrintf("BitcoinMiner(): Signing new block failed \n");
                  continue;
              }
  
              LogPrintf("CPUMiner : proof-of-stake block was signed %s \n", pblock->GetHash().ToString().c_str());
              SetThreadPriority(THREAD_PRIORITY_NORMAL);
              ProcessBlockFound(pblock, *pwallet, reservekey);
              SetThreadPriority(THREAD_PRIORITY_LOWEST);
  
              continue;
          }
  
          LogPrintf("Running KhrysusMiner with %u transactions in block (%u bytes)\n", pblock->vtx.size(),
              ::GetSerializeSize(*pblock, SER_NETWORK, PROTOCOL_VERSION));
  
          //
          // Search
          //
          int64_t nStart = GetTime();
          uint256 hashTarget = uint256().SetCompact(pblock->nBits);
          while (true) {
              unsigned int nHashesDone = 0;
  
              uint256 hash;
              while (true) {
                  hash = pblock->GetHash();
                  if (hash <= hashTarget) {
                      // Found a solution
                      SetThreadPriority(THREAD_PRIORITY_NORMAL);
                      LogPrintf("BitcoinMiner:\n");
                      LogPrintf("proof-of-work found  \n  hash: %s  \ntarget: %s\n", hash.GetHex(), hashTarget.GetHex());
                      ProcessBlockFound(pblock, *pwallet, reservekey);
                      SetThreadPriority(THREAD_PRIORITY_LOWEST);
  
                      // In regression test mode, stop mining after a block is found. This
                      // allows developers to controllably generate a block on demand.
                      if (Params().MineBlocksOnDemand())
                          throw boost::thread_interrupted();
  
                      break;
                  }
                  pblock->nNonce += 1;
                  nHashesDone += 1;
                  if ((pblock->nNonce & 0xFF) == 0)
                      break;
              }
  
              // Meter hashes/sec
              static int64_t nHashCounter;
              if (nHPSTimerStart == 0) {
                  nHPSTimerStart = GetTimeMillis();
                  nHashCounter = 0;
              } else
                  nHashCounter += nHashesDone;
              if (GetTimeMillis() - nHPSTimerStart > 4000) {
                  static CCriticalSection cs;
                  {
                      LOCK(cs);
                      if (GetTimeMillis() - nHPSTimerStart > 4000) {
                          dHashesPerSec = 1000.0 * nHashCounter / (GetTimeMillis() - nHPSTimerStart);
                          nHPSTimerStart = GetTimeMillis();
                          nHashCounter = 0;
                          static int64_t nLogTime;
                          if (GetTime() - nLogTime > 30 * 60) {
                              nLogTime = GetTime();
                              LogPrintf("hashmeter %6.0f khash/s\n", dHashesPerSec / 1000.0);
                          }
                      }
                  }
              }
  
              // Check for stop or if block needs to be rebuilt
              boost::this_thread::interruption_point();
              // Regtest mode doesn't require peers
              if (vNodes.empty() && Params().MiningRequiresPeers())
                  break;
              if (pblock->nNonce >= 0xffff0000)
                  break;
              if (mempool.GetTransactionsUpdated() != nTransactionsUpdatedLast && GetTime() - nStart > 60)
                  break;
              if (pindexPrev != chainActive.Tip())
                  break;
  
              // Update nTime every few seconds
              UpdateTime(pblock, pindexPrev);
              if (Params().AllowMinDifficultyBlocks()) {
                  // Changing pblock->nTime can change work required on testnet:
                  hashTarget.SetCompact(pblock->nBits);
              }
          }
      }
  }
  
  void static ThreadBitcoinMiner(void* parg)
  {
      boost::this_thread::interruption_point();
      CWallet* pwallet = (CWallet*)parg;
      try {
          BitcoinMiner(pwallet, false);
          boost::this_thread::interruption_point();
      } catch (std::exception& e) {
          LogPrintf("ThreadBitcoinMiner() exception");
      } catch (...) {
          LogPrintf("ThreadBitcoinMiner() exception");
      }
  
      LogPrintf("ThreadBitcoinMiner exiting\n");
  }
  
  void GenerateBitcoins(bool fGenerate, CWallet* pwallet, int nThreads)
  {
      static boost::thread_group* minerThreads = NULL;
      fGenerateBitcoins = fGenerate;
  
      if (nThreads < 0) {
          // In regtest threads defaults to 1
          if (Params().DefaultMinerThreads())
              nThreads = Params().DefaultMinerThreads();
          else
              nThreads = boost::thread::hardware_concurrency();
      }
  
      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(&ThreadBitcoinMiner, pwallet));
  }
  
  #endif // ENABLE_WALLET
  