public DoubleArray SmoothFourierReflectiveBC(double width)
        {
            Complex[] bed = new Complex[Length*2];
            //double norm = 1.0 / Math.Sqrt(2 * Math.PI * width * width);
            for (int i=0;i<Length;i++)
            {
                bed[i] = this[i];
                bed[Length*2-1-i] = this[i];
            }
            MathNet.Numerics.IntegralTransforms.Fourier.Forward(bed);
            for (int i = 0; i < Length * 2; i++)
            {
                double k = i;
                if (k>Length) k = Length*2 - i;
                k = k / (2*Length);
                double a2 = 2 * width * width * Math.PI * Math.PI * k * k;
                bed[i] *= Math.Exp(-a2);
            }
            MathNet.Numerics.IntegralTransforms.Fourier.Inverse(bed);
            DoubleArray da = new DoubleArray(Length);
            for (int i = 0; i < Length; i++)
            {
                da[i] = bed[i].Real;
            }
            return da;
        }