| sterf(3) | LAPACK | sterf(3) |
sterf - sterf: eig, QR iteration
subroutine dsterf (n, d, e, info)
DSTERF subroutine ssterf (n, d, e, info)
SSTERF
DSTERF
Purpose:
DSTERF computes all eigenvalues of a symmetric tridiagonal matrix
using the Pal-Walker-Kahan variant of the QL or QR algorithm.
Parameters
N is INTEGER
The order of the matrix. N >= 0.
D
D is DOUBLE PRECISION array, dimension (N)
On entry, the n diagonal elements of the tridiagonal matrix.
On exit, if INFO = 0, the eigenvalues in ascending order.
E
E is DOUBLE PRECISION array, dimension (N-1)
On entry, the (n-1) subdiagonal elements of the tridiagonal
matrix.
On exit, E has been destroyed.
INFO
INFO is INTEGER
= 0: successful exit
< 0: if INFO = -i, the i-th argument had an illegal value
> 0: the algorithm failed to find all of the eigenvalues in
a total of 30*N iterations; if INFO = i, then i
elements of E have not converged to zero.
Author
Univ. of California Berkeley
Univ. of Colorado Denver
NAG Ltd.
SSTERF
Purpose:
SSTERF computes all eigenvalues of a symmetric tridiagonal matrix
using the Pal-Walker-Kahan variant of the QL or QR algorithm.
Parameters
N is INTEGER
The order of the matrix. N >= 0.
D
D is REAL array, dimension (N)
On entry, the n diagonal elements of the tridiagonal matrix.
On exit, if INFO = 0, the eigenvalues in ascending order.
E
E is REAL array, dimension (N-1)
On entry, the (n-1) subdiagonal elements of the tridiagonal
matrix.
On exit, E has been destroyed.
INFO
INFO is INTEGER
= 0: successful exit
< 0: if INFO = -i, the i-th argument had an illegal value
> 0: the algorithm failed to find all of the eigenvalues in
a total of 30*N iterations; if INFO = i, then i
elements of E have not converged to zero.
Author
Univ. of California Berkeley
Univ. of Colorado Denver
NAG Ltd.
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| Thu Aug 7 2025 17:26:25 | Version 3.12.0 |