srecord noeq LCMerger_v3(LineCompReader lc1) {

  LineCompReader lc2;

  LineCompReader lcOut; // actually the same as lc1 now

  LCSortedPairIndex pairIndex;

  Map<S, Int> literalIndex;

  new IntBuffer lc2map;

  int newLiterals; // number of literals added compared to lc1

  int newPairs;

  int nOriginalLiterals, nOriginalPairs;

  int lc2PairCount;

  *(LineCompReader *lc1, LineCompReader *lc2) {}

  *(File ubcFile) {

    lcOut = lc1 = LineCompReader(ubcFile);

  }

  void add(File ubcFile) {

    //if (lc2 != null) fail("Can only run once for now");

    lc2 = new LineCompReader;

    lc2PairCount = 0;

    lcOut = lc1;

    nOriginalLiterals = l(lc1.literals);

    nOriginalPairs = l(lc1.pairs);

    newLiterals = newPairs = 0;

    printWithTime("Making literalIndex");

    literalIndex = indexList(lc1.literals);

    lc2.onPair = p -> { 

      if (lc2PairCount == 0) { initPhase2(); }

      ++lc2PairCount;

      long pAdjusted = twoIntsToLong(adjust2(firstIntFromLong(p)), adjust2(secondIntFromLong(p)));

      int iPair = pairIndex.get(pAdjusted);

      if (iPair < 0) { // new pair

        iPair = l(lc1.pairs);

        lc1.pairs.add(pAdjusted);

        ++newPairs;

      }

      lc2map.add(l(lcOut.literals)+iPair);

    };

    lc2.load(ubcFile);

    // copy files

    printWithTime("Merging files");

    lc1.versions = (LinkedHashMap) mapValues(lc1.versions, enc -> lmap adjust1(enc));

    for (S name, L<Int> encoding : lc2.versions) {

      if (lc1.versions.containsKey(name))

        continue with print("Warning: Duplicate file name " + name);

      lc1.versions.put(name, lmap adjust2(encoding));

    }

    printVars_str(+newLiterals, +newPairs, +lc2PairCount);

    print("Synergy factor: " + doubleRatio(lc2PairCount-newPairs, lc2PairCount));

  }

  // convert symbols from lc1

  int adjust1(int i) {

    if (i >= nOriginalLiterals)

      if (i >= nOriginalLiterals+nOriginalPairs)

        ret i+newLiterals+newPairs;

      else

        ret i+newLiterals;

    ret i;

  }

  int adjust2(int i) { ret lc2map.get(i); }

  void initPhase2 {

    // add lc2.literals to lc1.literals

    lc2map = new IntBuffer(l(lc2.literals) + l(lc2.pairs));

    printWithTime("Merging literals");

    for (int i = 0; i < l(lc2.literals); i++) {

      S c = lc2.literals.get(i);

      Int iLit = literalIndex.get(c);

      if (iLit == null) {

        iLit = addAndReturnIndex(lc1.literals, c);

        ++newLiterals;

        literalIndex.put(c, iLit);

      }

      lc2map.add(iLit);

    }

    // merge pairs

    printWithTime("Adjusting lc1 pairs");

    for i to nOriginalPairs: {

      long p = lc1.pairs.get(i);

      lc1.pairs.set(i, twoIntsToLong(adjust1(firstIntFromLong(p)), adjust1(secondIntFromLong(p))));

    }

    // Make index after adjustment

    printWithTime("Making pairIndex for " + nPairs(l(lc1.pairs)));

    pairIndex = new LCSortedPairIndex(lc1.pairs.toArray(), pairIndex);

    printWithTime("Merging pairs");

  }

}