private void performIntersect()

in src/main/java/org/apache/datasketches/theta/IntersectionImpl.java [424:482]
51 lines of code
13 McCabe index (conditional complexity)

  private void performIntersect(final Sketch sketchIn) {
    // curCount and input data are nonzero, match against HT
    assert curCount_ > 0 && !empty_;
    final long[] cacheIn = sketchIn.getCache();
    final int arrLongsIn = cacheIn.length;
    final long[] hashTable;
    if (wmem_ != null) {
      final int htLen = 1 << lgArrLongs_;
      hashTable = new long[htLen];
      wmem_.getLongArray(CONST_PREAMBLE_LONGS << 3, hashTable, 0, htLen);
    } else {
      hashTable = hashTable_;
    }
    //allocate space for matching
    final long[] matchSet = new long[ min(curCount_, sketchIn.getRetainedEntries(true)) ];

    int matchSetCount = 0;
    if (sketchIn.isOrdered()) {
      //ordered compact, which enables early stop
      for (int i = 0; i < arrLongsIn; i++ ) {
        final long hashIn = cacheIn[i];
        //if (hashIn <= 0L) continue;  //<= 0 should not happen
        if (hashIn >= thetaLong_) {
          break; //early stop assumes that hashes in input sketch are ordered!
        }
        final int foundIdx = hashSearch(hashTable, lgArrLongs_, hashIn);
        if (foundIdx == -1) { continue; }
        matchSet[matchSetCount++] = hashIn;
      }
    }
    else {
      //either unordered compact or hash table
      for (int i = 0; i < arrLongsIn; i++ ) {
        final long hashIn = cacheIn[i];
        if (hashIn <= 0L || hashIn >= thetaLong_) { continue; }
        final int foundIdx = hashSearch(hashTable, lgArrLongs_, hashIn);
        if (foundIdx == -1) { continue; }
        matchSet[matchSetCount++] = hashIn;
      }
    }
    //reduce effective array size to minimum
    curCount_ = matchSetCount;
    lgArrLongs_ = minLgHashTableSize(matchSetCount, ThetaUtil.REBUILD_THRESHOLD);
    if (wmem_ != null) {
      insertCurCount(wmem_, matchSetCount);
      insertLgArrLongs(wmem_, lgArrLongs_);
      wmem_.clear(CONST_PREAMBLE_LONGS << 3, 8 << lgArrLongs_); //clear for rebuild
    } else {
      Arrays.fill(hashTable_, 0, 1 << lgArrLongs_, 0L); //clear for rebuild
    }

    if (curCount_ > 0) {
      moveDataToTgt(matchSet, matchSetCount); //move matchSet to target
    } else {
      if (thetaLong_ == Long.MAX_VALUE) {
        empty_ = true;
      }
    }
  }