/// <summary>
/// Calculates the inverse matrix using Householder transformations
/// </summary>
public static M44d QrInverse(this M44d mat)
{
var qr = new Matrix <double>((double[])mat, 4, 4);
var diag = qr.QrFactorize();
return((M44d)(qr.QrInverse(diag).Data));
}