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EricDarve / numerical_linear_algebra

Julia code for the book Numerical Linear Algebra
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Notation for QR iteration #223

Closed Shengbo-Wang closed 3 years ago

Shengbo-Wang commented 3 years ago

The notation used in section QR iteration is a little confusing to me. We write T = Q^TAQ and A = QR where the Qs mean different things.

EricDarve commented 3 years ago

Where did you see this? Are these two notations used at the same time on the same page or section? It's OK to have A = QR in Chapter 5 and T = Q^T A Q in 6.2. These are standard notations. A = Q T Q^H is the Schur decomposition, for example.

EricDarve commented 3 years ago

I made some changes to distinguish the matrix Q_k in the iteration algorithms from the Q from the Schur decomposition.