Update compute_gyration_shape.cpp

  }

  // compute the shape parameters of the gyration tensor

  double sq_eigen_x = MathSpecial::square(evalues[0]);

  double sq_eigen_y = MathSpecial::square(evalues[1]);

  double sq_eigen_z = MathSpecial::square(evalues[2]);

  double nominator = MathSpecial::square(sq_eigen_x)

    + MathSpecial::square(sq_eigen_y)

    + MathSpecial::square(sq_eigen_z);

  double denominator = MathSpecial::square(sq_eigen_x+sq_eigen_y+sq_eigen_z);

  double nominator = MathSpecial::square(evalues[0])

    + MathSpecial::square(evalues[1])

    + MathSpecial::square(evalues[2]);

  double denominator = MathSpecial::square(evalues[0]+evalues[1]+evalues[2]);

  vector[0] = evalues[0];

  vector[1] = evalues[1];

  vector[2] = evalues[2];

  vector[3] = sq_eigen_z - 0.5*(sq_eigen_x + sq_eigen_y);

  vector[4] = sq_eigen_y - sq_eigen_x;

  vector[5] = 0.5*(3*nominator/denominator - 1.0);

  vector[3] = evalues[0] - 0.5*(evalues[1] + evalues[2]);

  vector[4] = evalues[1] - evalues[2];

  vector[5] = 1.5*nominator/denominator - 0.5;

}