stev - Man Page

subroutine dstev (jobz, n, d, e, z, ldz, work, info)
DSTEV computes the eigenvalues and, optionally, the left and/or right eigenvectors for OTHER matrices
subroutine sstev (jobz, n, d, e, z, ldz, work, info)
SSTEV computes the eigenvalues and, optionally, the left and/or right eigenvectors for OTHER matrices

DSTEV computes the eigenvalues and, optionally, the left and/or right eigenvectors for OTHER matrices  

Purpose:

 DSTEV computes all eigenvalues and, optionally, eigenvectors of a
 real symmetric tridiagonal matrix A.

Parameters

JOBZ

          JOBZ is CHARACTER*1
          = 'N':  Compute eigenvalues only;
          = 'V':  Compute eigenvalues and eigenvectors.

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
          A.
          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 A, stored in elements 1 to N-1 of E.
          On exit, the contents of E are destroyed.

Z

          Z is DOUBLE PRECISION array, dimension (LDZ, N)
          If JOBZ = 'V', then if INFO = 0, Z contains the orthonormal
          eigenvectors of the matrix A, with the i-th column of Z
          holding the eigenvector associated with D(i).
          If JOBZ = 'N', then Z is not referenced.

LDZ

          LDZ is INTEGER
          The leading dimension of the array Z.  LDZ >= 1, and if
          JOBZ = 'V', LDZ >= max(1,N).

WORK

          WORK is DOUBLE PRECISION array, dimension (max(1,2*N-2))
          If JOBZ = 'N', WORK is not referenced.

INFO

          INFO is INTEGER
          = 0:  successful exit
          < 0:  if INFO = -i, the i-th argument had an illegal value
          > 0:  if INFO = i, the algorithm failed to converge; i
                off-diagonal elements of E did not converge to zero.

Author

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

Definition at line 115 of file dstev.f.

SSTEV computes the eigenvalues and, optionally, the left and/or right eigenvectors for OTHER matrices  

Purpose:

 SSTEV computes all eigenvalues and, optionally, eigenvectors of a
 real symmetric tridiagonal matrix A.

Parameters

JOBZ

          JOBZ is CHARACTER*1
          = 'N':  Compute eigenvalues only;
          = 'V':  Compute eigenvalues and eigenvectors.

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
          A.
          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 A, stored in elements 1 to N-1 of E.
          On exit, the contents of E are destroyed.

Z

          Z is REAL array, dimension (LDZ, N)
          If JOBZ = 'V', then if INFO = 0, Z contains the orthonormal
          eigenvectors of the matrix A, with the i-th column of Z
          holding the eigenvector associated with D(i).
          If JOBZ = 'N', then Z is not referenced.

LDZ

          LDZ is INTEGER
          The leading dimension of the array Z.  LDZ >= 1, and if
          JOBZ = 'V', LDZ >= max(1,N).

WORK

          WORK is REAL array, dimension (max(1,2*N-2))
          If JOBZ = 'N', WORK is not referenced.

INFO

          INFO is INTEGER
          = 0:  successful exit
          < 0:  if INFO = -i, the i-th argument had an illegal value
          > 0:  if INFO = i, the algorithm failed to converge; i
                off-diagonal elements of E did not converge to zero.

Author

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

Definition at line 115 of file sstev.f.