assertBitEquals(x + y, a.get());
      }
    }
  }

  /**
   * getAndUpdate with subtract stores subtraction of value from current, and returns previous value
   */
  public void testGetAndUpdateWithSubtract() {
    for (double x : VALUES) {
      for (double y : VALUES) {
        AtomicDouble a = new AtomicDouble(x);
        double z = a.getAndUpdate(value -> value - y);
        assertBitEquals(x, z);

          assertBitEquals(x + y, aa.get(i));
        }
      }
    }
  }

  /** getAndUpdate subtracts given value to current, and returns previous value */
  public void testGetAndUpdateWithSubtract() {
    AtomicDoubleArray aa = new AtomicDoubleArray(SIZE);
    for (int i : new int[] {0, SIZE - 1}) {
      for (double x : VALUES) {
        for (double y : VALUES) {
          aa.set(i, x);