sclass InvestigateNonTransientGraph {

  MetaTransformer mt;

  Map back = identityHashMap();

  new MultiSet<O> objectsBySize;

  new MultiMap<Class, O> objectsByClass;

  new MultiSet<S> objectsByDynClass;

  *() {

    mt = metaTransformer_collectionAndMap();

    mt.add(new MTSH_nonTransientFields);

    mt.avoidCycles();

    mt.markPointer = (a, b) -> {

      putIfNotThere(back, b, a);

    };

  }

  void scan(O root) {

    VStack.Computable v = mt.new visit_vstackComputable(o -> {

      objectsBySize.add(o.getClass(), clampToInt(unsafe_sizeOf(o)));

      objectsByClass.put(o.getClass(), o);

      if (o instanceof DynamicObject)

        objectsByDynClass.add(shortDynClassName(o));

    }, root);

    vstackCompute(v);

  }

  void printResults() {

    print("Seen objects: " + n2(mt.seen));

    print();

    print("Most popular classes:");

    print(multiSetToLines(multiMapToMultiSet(objectsByClass), 20));

    print();

    print("Total bytes per class:");

    print(multiSetToLines(objectsBySize, 20));

    if (!empty(objectsByDynClass)) {

      print("Popular dynamic classes:");

      print(multiSetToLines(objectsByDynClass, 20));

    }

  }

  <A> L<A> biggestOfClass(Class<A> c) {

    ret sortedByCalculatedFieldDesc unsafe_objectSize((Cl<A>) objectsByClass.get(c));

  }

  void printBiggestByteArrays() {

    for (var array : takeFirst(2, biggestOfClass(byteArrayType()))) {

      print("Byte array " + n2_l(array));

      O o = array;

      repeat 10 {

        if (o == null) break;

        o = back.get(o);

        print("  <= " + className/*shortenedToStringWithClass*/(o));

      }

    }

  }

}