has characteristic Krylov subspace projection method conjugate gradient method 2011-06-10 urn:issn:0091-0635 AZ CG Conjugate gradient method is an algorithm for the numerical solution of particular systems of linear equations, namely those whose matrix is symmetric and positive-definite. The conjugate gradient method is an iterative method, so it can be applied to sparse systems that are too large to be handled by direct methods. Such systems often arise when numerically solving partial differential equations. symmetricity of matrix