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. >
