function [x,k]=gmres(A,b,m,toll,x0)r0=b-A*x0;  nr0=norm(r0,2);if nr0 ~= 0  v1=r0/nr0;   V=[v1];   H=[];   k=0;   residual=1;  while k <= m-1 & residual > toll,         [k,V,H] = GSarnoldi(A,m,k,V,H);     [nr,nc]=size(H);        y=(H'*H) \ (H'*nr0*[1;zeros(nr-1,1)]);    x=x0+V(:,1:nc)*y;       residual = norm(b-A*x,2)/nr0;   endelse  x=x0;endreturn