Implement absolute threshold for early deflation in Schur algorithm #1565
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Fix #1528.
The issue was that, during the deflation step, the diagonal element of the matrix were all zero so the deflation never triggered based on this line :
t[(n, m)].clone().norm1() <= eps.clone() * (t[(n, n)].clone().norm1() + t[(m, m)].clone().norm1())added a check to compare an off-diag element to an absolute very small value
(eps.clone() * eps.clone())the eigenvalues found are correctly :
Complex { re: -0.8611363115940531, im: 0.0 },
Complex { re: 0.8611363115940531, im: 0.0 },
Complex { re: -0.33998104358485637, im: 0.0 },
Complex { re: 0.33998104358485637, im: 0.0 }