Solution of G b = u

Use your modified numerical recipes routines from 3.2.1 to solve the matrix equation G*b=u for b, taking the program in Appendix E as a model. Note that, for this, you will have to declare (and free!) a dmatrix LU with the same dimensions as G, a dvector b with the same dimensions as u, an ivector indx with the same dimensions as b, and a dummy double variable sgn. For debugging purposes, we highly recommend that you include the ``Testing G*b=u?'' part of the code from the appendix.

Note that, at this stage, your code should still output the same energies because we have not yet put the final prediction in Rho$_{it+1}$. Finally, once you are certain that the linear solver is functioning properly, comment out the test G*b=u part.