ISUPPZ value in LAPACK DSYEVR
I want to calculate my own system to some big real symmetric matrices and find a DSYEVR routine that should suit my needs.
dsyevr (JOBZ, RANGE, UPLO, N, A, LDA, VL, VU, IL, IU, ABSTOL, M, W, Z, LDZ, ISUPPZ, WORK, LWORK, IWORK, LIWORK, INFO)
While enabling and testing this subroutine, I noticed a parameter
, which is an integer array of length
, where it
indicates the number of eigenvalues calculated (which can vary depending on the input).
According to the documentation, an array
defines the position of non-zero elements in an array of eigenvectors
. That is, in particular,
the eigenvector has nonzero elements between the positions
Now I have a problem that this does not match my observations. For example. when calculating its own system to an exemplary size system, the
second eigenvector has, according to
, only nonzero elements between the positions
. Looking at the eigenvector, I see that this is clearly not the case, and comparing with
, I clearly see that it should not be either.
Actually, its own system
is basically the same as the original system designed for
. As a result, I am assuming there is nothing wrong overall.
So what is the actual meaning of the parameter
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