docs: private DoubleMinMax exactMinMax(Relation<O> relation, DistanceQuery<O> distFunc) {
      final FiniteProgress progress = LOG.isVerbose() ? new FiniteProgress("Exact fitting distance computations", relation.size(), LOG) : null;
      DoubleMinMax minmax = new DoubleMinMax();
      // find exact minimum and maximum first.
      for(DBIDIter iditer = relation.iterDBIDs(); iditer.valid(); iditer.advance()) {
        for(DBIDIter iditer2 = relation.iterDBIDs(); iditer2.valid(); iditer2.advance()) {
          // skip the point itself.
          if(DBIDUtil.equal(iditer, iditer2)) {
            continue;
          }
          double d = distFunc.distance(iditer, iditer2);
          minmax.put(d);
        }
        LOG.incrementProcessed(progress);
      }
      LOG.ensureCompleted(progress);
      return minmax;
    }