# Tag Info

Wolfgang Bangerth's answer already says almost everything, but another subtle detail is that GMRES/MINRES minimize the norm of the residual, i.e., $\|Ax_k-b\|$, while CG minimizes the (A-)norm of the error, i.e., $\|x_*-x_k\|_A$. In most cases what you really want to minimize is the error, and the residual serves as an imperfect proxy: recall that by the ...