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Re: Problem with Schur decomposition
From: |
Patrick Alken |
Subject: |
Re: Problem with Schur decomposition |
Date: |
Tue, 18 May 2021 20:33:30 -0600 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.8.1 |
Note that the documentation says:
"If T is desired, it is stored in the upper portion of A on output".
This means that the gsl_eigen_nonsymm / gsl_eigen_nonsymm_Z functions do
not zero out the lower portion of the output matrix. The lower portion
of A is used as temporary workspace by the eigenvalue solver, so the
values stored here should not be referenced. You can explicitly set the
lower portion of A to zero with the function:
gsl_linalg_hessenberg_set_zero()
to get the behavior you want.
Patrick
On 5/18/21 3:05 PM, david allen wrote:
> What is supposed to be a upper quasi-triangular matrix has non-zero
> elements below the first sub-diagonal. This is demonstrated in the
> attached file. Computer and OS information are also in the file.
>