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A=[3 1 10 4;1 0 1 2;2 1 1 0;-1 1 3 1];
%M=[5 2 3;2 8 4;3 4 9]
%A=[1 0 1;0 1 1/4;-1 1 3 1];
b=A*[1 1 1 1]';
[Q,H] = Arnoldi(A,4,b);
[x,flag,relres,iter]=gmres(A,b)
nb=norm(b);
for i=1:4
e1=zeros(i+1,1);
e1(1,1)=1;
i
Hi=H(1:i+1,1:i)
AA=Hi'*Hi;
bb=nb*Hi'*e1;
i
y=AA\bb
Q1=Q(:,1:i)
xx(:,i)=Q(:,1:i)*y
rr(i)=norm(b-A*xx(:,i))
end
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