assertTrue(Double.isNaN(DoubleMath.log2(Double.NaN)));
  }

  @GwtIncompatible // StrictMath
  private strictfp double trueLog2(double d) {
    double trueLog2 = StrictMath.log(d) / StrictMath.log(2);
    // increment until it's >= the true value
    while (StrictMath.pow(2.0, trueLog2) < d) {
      trueLog2 = StrictMath.nextUp(trueLog2);
    }
    // decrement until it's <= the true value

    assertTrue(Double.isNaN(DoubleMath.log2(Double.NaN)));
  }

  @GwtIncompatible // StrictMath
  private strictfp double trueLog2(double d) {
    double trueLog2 = StrictMath.log(d) / StrictMath.log(2);
    // increment until it's >= the true value
    while (StrictMath.pow(2.0, trueLog2) < d) {
      trueLog2 = StrictMath.nextUp(trueLog2);
    }
    // decrement until it's <= the true value