P=[3/2 1 0; -1 3/2 0; 1 -1 3/2];
x0=[1 1 1];
b=[1 1 1];

NN=10000;
TOL=10^(-15);
n=3;
k=1;

while k<=NN
	for i=1:n
		s=P(i,[1:n])*x0([1:n])';
		x(i)=[s+b(i)]/2;
	end
	if norm(x-x0)<TOL
		break
	end
	k=k+1;
	x0=x;
end
if k>NN
	fprintf('Maximum number of iterations exceeded\n')
	x=NaN;
end
k
x