MATLAB: Report bug on document of gmres

Question

The example code for gmres with preconditioner has bug: the relative residual to plot from resvec should be resvec/norm(preconditioner\b), not resvec/norm(b).

A simple check is the relative residual should be 1 when interation = 0, since norm(Ax-b)/norm(b) = norm(b)/norm(b) = 1.

Answer 1

On the bottom of the documentation for any function, click on one of the 5 stars. It will bring up a box that asks you why you gave that star rating and you can tell your story. It will go right to the documentation people at the Mathworks, who would contact the developer for that function if necessary.

Or you can click this link: Bug Reports

Or simply call them on the phone, or email them at support @ mathworks . com