zlaed7.f (3)  Linux Manuals
NAME
zlaed7.f 
SYNOPSIS
Functions/Subroutines
subroutine zlaed7 (N, CUTPNT, QSIZ, TLVLS, CURLVL, CURPBM, D, Q, LDQ, RHO, INDXQ, QSTORE, QPTR, PRMPTR, PERM, GIVPTR, GIVCOL, GIVNUM, WORK, RWORK, IWORK, INFO)
ZLAED7 used by sstedc. Computes the updated eigensystem of a diagonal matrix after modification by a rankone symmetric matrix. Used when the original matrix is dense.
Function/Subroutine Documentation
subroutine zlaed7 (integerN, integerCUTPNT, integerQSIZ, integerTLVLS, integerCURLVL, integerCURPBM, double precision, dimension( * )D, complex*16, dimension( ldq, * )Q, integerLDQ, double precisionRHO, integer, dimension( * )INDXQ, double precision, dimension( * )QSTORE, integer, dimension( * )QPTR, integer, dimension( * )PRMPTR, integer, dimension( * )PERM, integer, dimension( * )GIVPTR, integer, dimension( 2, * )GIVCOL, double precision, dimension( 2, * )GIVNUM, complex*16, dimension( * )WORK, double precision, dimension( * )RWORK, integer, dimension( * )IWORK, integerINFO)
ZLAED7 used by sstedc. Computes the updated eigensystem of a diagonal matrix after modification by a rankone symmetric matrix. Used when the original matrix is dense.
Purpose:

ZLAED7 computes the updated eigensystem of a diagonal matrix after modification by a rankone symmetric matrix. This routine is used only for the eigenproblem which requires all eigenvalues and optionally eigenvectors of a dense or banded Hermitian matrix that has been reduced to tridiagonal form. T = Q(in) ( D(in) + RHO * Z*Z**H ) Q**H(in) = Q(out) * D(out) * Q**H(out) where Z = Q**Hu, u is a vector of length N with ones in the CUTPNT and CUTPNT + 1 th elements and zeros elsewhere. The eigenvectors of the original matrix are stored in Q, and the eigenvalues are in D. The algorithm consists of three stages: The first stage consists of deflating the size of the problem when there are multiple eigenvalues or if there is a zero in the Z vector. For each such occurence the dimension of the secular equation problem is reduced by one. This stage is performed by the routine DLAED2. The second stage consists of calculating the updated eigenvalues. This is done by finding the roots of the secular equation via the routine DLAED4 (as called by SLAED3). This routine also calculates the eigenvectors of the current problem. The final stage consists of computing the updated eigenvectors directly using the updated eigenvalues. The eigenvectors for the current problem are multiplied with the eigenvectors from the overall problem.
Parameters:

N
N is INTEGER The dimension of the symmetric tridiagonal matrix. N >= 0.
CUTPNTCUTPNT is INTEGER Contains the location of the last eigenvalue in the leading submatrix. min(1,N) <= CUTPNT <= N.
QSIZQSIZ is INTEGER The dimension of the unitary matrix used to reduce the full matrix to tridiagonal form. QSIZ >= N.
TLVLSTLVLS is INTEGER The total number of merging levels in the overall divide and conquer tree.
CURLVLCURLVL is INTEGER The current level in the overall merge routine, 0 <= curlvl <= tlvls.
CURPBMCURPBM is INTEGER The current problem in the current level in the overall merge routine (counting from upper left to lower right).
DD is DOUBLE PRECISION array, dimension (N) On entry, the eigenvalues of the rank1perturbed matrix. On exit, the eigenvalues of the repaired matrix.
QQ is COMPLEX*16 array, dimension (LDQ,N) On entry, the eigenvectors of the rank1perturbed matrix. On exit, the eigenvectors of the repaired tridiagonal matrix.
LDQLDQ is INTEGER The leading dimension of the array Q. LDQ >= max(1,N).
RHORHO is DOUBLE PRECISION Contains the subdiagonal element used to create the rank1 modification.
INDXQINDXQ is INTEGER array, dimension (N) This contains the permutation which will reintegrate the subproblem just solved back into sorted order, ie. D( INDXQ( I = 1, N ) ) will be in ascending order.
IWORKIWORK is INTEGER array, dimension (4*N)
RWORKRWORK is DOUBLE PRECISION array, dimension (3*N+2*QSIZ*N)
WORKWORK is COMPLEX*16 array, dimension (QSIZ*N)
QSTOREQSTORE is DOUBLE PRECISION array, dimension (N**2+1) Stores eigenvectors of submatrices encountered during divide and conquer, packed together. QPTR points to beginning of the submatrices.
QPTRQPTR is INTEGER array, dimension (N+2) List of indices pointing to beginning of submatrices stored in QSTORE. The submatrices are numbered starting at the bottom left of the divide and conquer tree, from left to right and bottom to top.
PRMPTRPRMPTR is INTEGER array, dimension (N lg N) Contains a list of pointers which indicate where in PERM a level's permutation is stored. PRMPTR(i+1)  PRMPTR(i) indicates the size of the permutation and also the size of the full, nondeflated problem.
PERMPERM is INTEGER array, dimension (N lg N) Contains the permutations (from deflation and sorting) to be applied to each eigenblock.
GIVPTRGIVPTR is INTEGER array, dimension (N lg N) Contains a list of pointers which indicate where in GIVCOL a level's Givens rotations are stored. GIVPTR(i+1)  GIVPTR(i) indicates the number of Givens rotations.
GIVCOLGIVCOL is INTEGER array, dimension (2, N lg N) Each pair of numbers indicates a pair of columns to take place in a Givens rotation.
GIVNUMGIVNUM is DOUBLE PRECISION array, dimension (2, N lg N) Each number indicates the S value to be used in the corresponding Givens rotation.
INFOINFO is INTEGER = 0: successful exit. < 0: if INFO = i, the ith argument had an illegal value. > 0: if INFO = 1, an eigenvalue did not converge
Author:

Univ. of Tennessee
Univ. of California Berkeley
Univ. of Colorado Denver
NAG Ltd.
Date:
 September 2012
Definition at line 247 of file zlaed7.f.
Author
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