check for diagonal matrices in find-diag-in-e-basis #857
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It seems that LAPACK becomes unstable on ARM when attempting to find the eigenvectors and eigenvalues of a diagonal matrix. This instability is triggered in find-diagonalizer-in-e-basis. The operation becomes trivial when run on a diagonal matrix, so we check for this and return the identity to avoid making a potentially unstable LAPACK call. Fixes quil-lang#842.
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Sep 30, 2022
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It seems that LAPACK becomes unstable on ARM when attempting to find the eigenvectors and eigenvalues of a diagonal matrix. This instability is triggered in find-diagonalizer-in-e-basis. The operation becomes trivial when run on a diagonal matrix, so we check for this and return the identity to avoid making a potentially unstable LAPACK call.
Fixes #842.