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sterf(3) LAPACK sterf(3)

NAME

sterf - sterf: eig, QR iteration

SYNOPSIS

Functions


subroutine dsterf (n, d, e, info)
DSTERF subroutine ssterf (n, d, e, info)
SSTERF

Detailed Description

Function Documentation

subroutine dsterf (integer n, double precision, dimension( * ) d, double precision, dimension( * ) e, integer info)

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 



          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 Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

subroutine ssterf (integer n, real, dimension( * ) d, real, dimension( * ) e, integer info)

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 



          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 Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

Author

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Tue Jan 28 2025 00:54:31 Version 3.12.0