Antonio Sanchez 3ee06ec52f Fix real schur and polynomial solver. ...

For certain inputs, the real schur decomposition might get stuck in a cycle.
Exceptional shifts are supposed to knock us out of that - but previously
they were only ever applied at iteration 10 and 30, which doesn't help if
the cycle starts after cycle 30.  Modified to apply a shift every 16 iterations
(for reference, LAPACK seems to do it every 6 iterations).

Also added an assert in polynomial solver to verify that the schur decomposition
was successful.

Fixes #2633.

2024-02-16 13:11:54 -08:00

4.1 KiB

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