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

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

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

.PP
.nf
 DSTEDC 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 DSYTRD or DSPTRD or DSBTRD 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 DOUBLE PRECISION 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 DOUBLE PRECISION 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 DOUBLE PRECISION 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 DOUBLE PRECISION 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 \fBdstedc\&.f\fP\&.
.SH "Author"
.PP 
Generated automatically by Doxygen for LAPACK from the source code\&.