gk     = (n/(c'*x))*c - ones(n,1)./x;
Xgk    = diag(x)*gk;
Ak     = A*diag(x);
Mk     = Ak*Ak';
yk     = Mk\(Ak*Xgk);
pk     = Xgk-Ak'*yk;
normpk = norm(pk)
y      = ((c'*x)/n)*yk;
x      = x.*(ones(n,1)-(.5/norm(pk))*pk);
potenf = n*log(c'*x+1)-ones(n,1)'*log(x)

