// result than multiplying by everySixteenthFactorial[n >> 4] directly.
      double accum = 1.0;
      for (int i = 1 + (n & ~0xf); i <= n; i++) {
        accum *= i;
      }
      return accum * everySixteenthFactorial[n >> 4];
    }
  }

  @VisibleForTesting static final int MAX_FACTORIAL = 170;

  @VisibleForTesting
  static final double[] everySixteenthFactorial = {
    0x1.0p0,
    0x1.30777758p44,

      // result than multiplying by everySixteenthFactorial[n >> 4] directly.
      double accum = 1.0;
      for (int i = 1 + (n & ~0xf); i <= n; i++) {
        accum *= i;
      }
      return accum * everySixteenthFactorial[n >> 4];
    }
  }

  @VisibleForTesting static final int MAX_FACTORIAL = 170;

  @VisibleForTesting
  static final double[] everySixteenthFactorial = {
    0x1.0p0,
    0x1.30777758p44,

  }

  public void testConstantsEverySixteenthFactorial() {
    for (int i = 0, n = 0; n <= DoubleMath.MAX_FACTORIAL; i++, n += 16) {
      assertEquals(
          BigIntegerMath.factorial(n).doubleValue(), DoubleMath.everySixteenthFactorial[i]);
    }
  }

  @GwtIncompatible // DoubleMath.roundToInt(double, RoundingMode)
  public void testRoundIntegralDoubleToInt() {
    for (double d : INTEGRAL_DOUBLE_CANDIDATES) {