table of contents
/home/abuild/rpmbuild/BUILD/lapack-3.12.0/SRC/slarrj.f(3) | Library Functions Manual | /home/abuild/rpmbuild/BUILD/lapack-3.12.0/SRC/slarrj.f(3) |
NAME¶
/home/abuild/rpmbuild/BUILD/lapack-3.12.0/SRC/slarrj.f
SYNOPSIS¶
Functions/Subroutines¶
subroutine SLARRJ (n, d, e2, ifirst, ilast, rtol, offset,
w, werr, work, iwork, pivmin, spdiam, info)
SLARRJ performs refinement of the initial estimates of the eigenvalues
of the matrix T.
Function/Subroutine Documentation¶
subroutine SLARRJ (integer n, real, dimension( * ) d, real, dimension( * ) e2, integer ifirst, integer ilast, real rtol, integer offset, real, dimension( * ) w, real, dimension( * ) werr, real, dimension( * ) work, integer, dimension( * ) iwork, real pivmin, real spdiam, integer info)¶
SLARRJ performs refinement of the initial estimates of the eigenvalues of the matrix T.
Purpose:
!> !> Given the initial eigenvalue approximations of T, SLARRJ !> does bisection to refine the eigenvalues of T, !> W( IFIRST-OFFSET ) through W( ILAST-OFFSET ), to more accuracy. Initial !> guesses for these eigenvalues are input in W, the corresponding estimate !> of the error in these guesses in WERR. During bisection, intervals !> [left, right] are maintained by storing their mid-points and !> semi-widths in the arrays W and WERR respectively. !>
Parameters
N
!> N is INTEGER !> The order of the matrix. !>
D
!> D is REAL array, dimension (N) !> The N diagonal elements of T. !>
E2
!> E2 is REAL array, dimension (N-1) !> The Squares of the (N-1) subdiagonal elements of T. !>
IFIRST
!> IFIRST is INTEGER !> The index of the first eigenvalue to be computed. !>
ILAST
!> ILAST is INTEGER !> The index of the last eigenvalue to be computed. !>
RTOL
!> RTOL is REAL !> Tolerance for the convergence of the bisection intervals. !> An interval [LEFT,RIGHT] has converged if !> RIGHT-LEFT < RTOL*MAX(|LEFT|,|RIGHT|). !>
OFFSET
!> OFFSET is INTEGER !> Offset for the arrays W and WERR, i.e., the IFIRST-OFFSET !> through ILAST-OFFSET elements of these arrays are to be used. !>
W
!> W is REAL array, dimension (N) !> On input, W( IFIRST-OFFSET ) through W( ILAST-OFFSET ) are !> estimates of the eigenvalues of L D L^T indexed IFIRST through !> ILAST. !> On output, these estimates are refined. !>
WERR
!> WERR is REAL array, dimension (N) !> On input, WERR( IFIRST-OFFSET ) through WERR( ILAST-OFFSET ) are !> the errors in the estimates of the corresponding elements in W. !> On output, these errors are refined. !>
WORK
!> WORK is REAL array, dimension (2*N) !> Workspace. !>
IWORK
!> IWORK is INTEGER array, dimension (2*N) !> Workspace. !>
PIVMIN
!> PIVMIN is REAL !> The minimum pivot in the Sturm sequence for T. !>
SPDIAM
!> SPDIAM is REAL !> The spectral diameter of T. !>
INFO
!> INFO is INTEGER !> Error flag. !>
Author
Univ. of Tennessee
Univ. of California Berkeley
Univ. of Colorado Denver
NAG Ltd.
Contributors:
Beresford Parlett, University of California, Berkeley,
USA
Jim Demmel, University of California, Berkeley, USA
Inderjit Dhillon, University of Texas, Austin, USA
Osni Marques, LBNL/NERSC, USA
Christof Voemel, University of California, Berkeley, USA
Jim Demmel, University of California, Berkeley, USA
Inderjit Dhillon, University of Texas, Austin, USA
Osni Marques, LBNL/NERSC, USA
Christof Voemel, University of California, Berkeley, USA
Definition at line 165 of file slarrj.f.
Author¶
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