.TH "SRC/sstedc.f" 3 "Version 3.12.0" "LAPACK" \" -*- nroff -*-
.ad l
.nh
.SH NAME
SRC/sstedc.f
.SH SYNOPSIS
.br
.PP
.SS "Functions/Subroutines"

.in +1c
.ti -1c
.RI "subroutine \fBsstedc\fP (compz, n, d, e, z, ldz, work, lwork, iwork, liwork, info)"
.br
.RI "\fBSSTEDC\fP "
.in -1c
.SH "Function/Subroutine Documentation"
.PP 
.SS "subroutine sstedc (character compz, integer n, real, dimension( * ) d, real, dimension( * ) e, real, dimension( ldz, * ) z, integer ldz, real, dimension( * ) work, integer lwork, integer, dimension( * ) iwork, integer liwork, integer info)"

.PP
\fBSSTEDC\fP  
.PP
\fBPurpose:\fP
.RS 4

.PP
.nf
!>
!> SSTEDC computes all eigenvalues and, optionally, eigenvectors of a
!> symmetric tridiagonal matrix using the divide and conquer method\&.
!> The eigenvectors of a full or band real symmetric matrix can also be
!> found if SSYTRD or SSPTRD or SSBTRD has been used to reduce this
!> matrix to tridiagonal form\&.
!>
!> 
.fi
.PP
 
.RE
.PP
\fBParameters\fP
.RS 4
\fICOMPZ\fP 
.PP
.nf
!>          COMPZ is CHARACTER*1
!>          = 'N':  Compute eigenvalues only\&.
!>          = 'I':  Compute eigenvectors of tridiagonal matrix also\&.
!>          = 'V':  Compute eigenvectors of original dense symmetric
!>                  matrix also\&.  On entry, Z contains the orthogonal
!>                  matrix used to reduce the original matrix to
!>                  tridiagonal form\&.
!> 
.fi
.PP
.br
\fIN\fP 
.PP
.nf
!>          N is INTEGER
!>          The dimension of the symmetric tridiagonal matrix\&.  N >= 0\&.
!> 
.fi
.PP
.br
\fID\fP 
.PP
.nf
!>          D is REAL array, dimension (N)
!>          On entry, the diagonal elements of the tridiagonal matrix\&.
!>          On exit, if INFO = 0, the eigenvalues in ascending order\&.
!> 
.fi
.PP
.br
\fIE\fP 
.PP
.nf
!>          E is REAL array, dimension (N-1)
!>          On entry, the subdiagonal elements of the tridiagonal matrix\&.
!>          On exit, E has been destroyed\&.
!> 
.fi
.PP
.br
\fIZ\fP 
.PP
.nf
!>          Z is REAL array, dimension (LDZ,N)
!>          On entry, if COMPZ = 'V', then Z contains the orthogonal
!>          matrix used in the reduction to tridiagonal form\&.
!>          On exit, if INFO = 0, then if COMPZ = 'V', Z contains the
!>          orthonormal eigenvectors of the original symmetric matrix,
!>          and if COMPZ = 'I', Z contains the orthonormal eigenvectors
!>          of the symmetric tridiagonal matrix\&.
!>          If  COMPZ = 'N', then Z is not referenced\&.
!> 
.fi
.PP
.br
\fILDZ\fP 
.PP
.nf
!>          LDZ is INTEGER
!>          The leading dimension of the array Z\&.  LDZ >= 1\&.
!>          If eigenvectors are desired, then LDZ >= max(1,N)\&.
!> 
.fi
.PP
.br
\fIWORK\fP 
.PP
.nf
!>          WORK is REAL array, dimension (MAX(1,LWORK))
!>          On exit, if INFO = 0, WORK(1) returns the optimal LWORK\&.
!> 
.fi
.PP
.br
\fILWORK\fP 
.PP
.nf
!>          LWORK is INTEGER
!>          The dimension of the array WORK\&.
!>          If COMPZ = 'N' or N <= 1 then LWORK must be at least 1\&.
!>          If COMPZ = 'V' and N > 1 then LWORK must be at least
!>                         ( 1 + 3*N + 2*N*lg N + 4*N**2 ),
!>                         where lg( N ) = smallest integer k such
!>                         that 2**k >= N\&.
!>          If COMPZ = 'I' and N > 1 then LWORK must be at least
!>                         ( 1 + 4*N + N**2 )\&.
!>          Note that for COMPZ = 'I' or 'V', then if N is less than or
!>          equal to the minimum divide size, usually 25, then LWORK need
!>          only be max(1,2*(N-1))\&.
!>
!>          If LWORK = -1, then a workspace query is assumed; the routine
!>          only calculates the optimal size of the WORK array, returns
!>          this value as the first entry of the WORK array, and no error
!>          message related to LWORK is issued by XERBLA\&.
!> 
.fi
.PP
.br
\fIIWORK\fP 
.PP
.nf
!>          IWORK is INTEGER array, dimension (MAX(1,LIWORK))
!>          On exit, if INFO = 0, IWORK(1) returns the optimal LIWORK\&.
!> 
.fi
.PP
.br
\fILIWORK\fP 
.PP
.nf
!>          LIWORK is INTEGER
!>          The dimension of the array IWORK\&.
!>          If COMPZ = 'N' or N <= 1 then LIWORK must be at least 1\&.
!>          If COMPZ = 'V' and N > 1 then LIWORK must be at least
!>                         ( 6 + 6*N + 5*N*lg N )\&.
!>          If COMPZ = 'I' and N > 1 then LIWORK must be at least
!>                         ( 3 + 5*N )\&.
!>          Note that for COMPZ = 'I' or 'V', then if N is less than or
!>          equal to the minimum divide size, usually 25, then LIWORK
!>          need only be 1\&.
!>
!>          If LIWORK = -1, then a workspace query is assumed; the
!>          routine only calculates the optimal size of the IWORK array,
!>          returns this value as the first entry of the IWORK array, and
!>          no error message related to LIWORK is issued by XERBLA\&.
!> 
.fi
.PP
.br
\fIINFO\fP 
.PP
.nf
!>          INFO is INTEGER
!>          = 0:  successful exit\&.
!>          < 0:  if INFO = -i, the i-th argument had an illegal value\&.
!>          > 0:  The algorithm failed to compute an eigenvalue while
!>                working on the submatrix lying in rows and columns
!>                INFO/(N+1) through mod(INFO,N+1)\&.
!> 
.fi
.PP
 
.RE
.PP
\fBAuthor\fP
.RS 4
Univ\&. of Tennessee 

.PP
Univ\&. of California Berkeley 

.PP
Univ\&. of Colorado Denver 

.PP
NAG Ltd\&. 
.RE
.PP
\fBContributors:\fP
.RS 4
Jeff Rutter, Computer Science Division, University of California at Berkeley, USA 
.br
 Modified by Francoise Tisseur, University of Tennessee 
.RE
.PP

.PP
Definition at line \fB180\fP of file \fBsstedc\&.f\fP\&.
.SH "Author"
.PP 
Generated automatically by Doxygen for LAPACK from the source code\&.