Preconditioning conjugate gradient with symmetric algebraic reconstruction technique (ART) in computerized tomography Original Research Article

We apply the conjugate gradient method to the system View the MathML source where Cω=(D+ωL)D−1/2 and AAt=L+D+Lt. This corresponds to applying CG to the generalized least square problem View the MathML source We use an efficient way to compute the expressions AtCω−tr and Cω−1Aw using only the rows of A.