Slightly tangential: This is how I visualise how the behaviour of the QR algorithm varies over all possible PSD matrices: https://en.wikipedia.org/wiki/QR_algor

Slightly tangential: This is how I visualise how the behaviour of the QR algorithm varies over all possible PSD matrices: https://en.wikipedia.org/wiki/QR_algorithm#Visualization https://en.wikipedia.org/wiki/QR_algorithm#Visualization In this case, it's less important to understand the convoluted structure of some code, than to understand how a simple but opaque algorithm behaves in general.