docs: protected static double getMinDist(DBIDArrayIter j, DistanceQuery<?> distQ, DBIDArrayIter mi, WritableDoubleDataStore mindist) {
      double prev = mindist.doubleValue(j);
      if(Double.isNaN(prev)) { // NaN = unknown
        prev = Double.POSITIVE_INFINITY;
        for(mi.seek(0); mi.valid(); mi.advance()) {
          double d = distQ.distance(j, mi);
          prev = d < prev ? d : prev;
        }
        mindist.putDouble(j, prev);
      }
      return prev;
    }