LAPACK
3.4.2
LAPACK: Linear Algebra PACKage

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Functions/Subroutines  
subroutine  claed7 (N, CUTPNT, QSIZ, TLVLS, CURLVL, CURPBM, D, Q, LDQ, RHO, INDXQ, QSTORE, QPTR, PRMPTR, PERM, GIVPTR, GIVCOL, GIVNUM, WORK, RWORK, IWORK, INFO) 
CLAED7 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. 
subroutine claed7  (  integer  N, 
integer  CUTPNT,  
integer  QSIZ,  
integer  TLVLS,  
integer  CURLVL,  
integer  CURPBM,  
real, dimension( * )  D,  
complex, dimension( ldq, * )  Q,  
integer  LDQ,  
real  RHO,  
integer, dimension( * )  INDXQ,  
real, dimension( * )  QSTORE,  
integer, dimension( * )  QPTR,  
integer, dimension( * )  PRMPTR,  
integer, dimension( * )  PERM,  
integer, dimension( * )  GIVPTR,  
integer, dimension( 2, * )  GIVCOL,  
real, dimension( 2, * )  GIVNUM,  
complex, dimension( * )  WORK,  
real, dimension( * )  RWORK,  
integer, dimension( * )  IWORK,  
integer  INFO  
) 
CLAED7 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.
Download CLAED7 + dependencies [TGZ] [ZIP] [TXT]CLAED7 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 SLAED2. The second stage consists of calculating the updated eigenvalues. This is done by finding the roots of the secular equation via the routine SLAED4 (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.
[in]  N  N is INTEGER The dimension of the symmetric tridiagonal matrix. N >= 0. 
[in]  CUTPNT  CUTPNT is INTEGER Contains the location of the last eigenvalue in the leading submatrix. min(1,N) <= CUTPNT <= N. 
[in]  QSIZ  QSIZ is INTEGER The dimension of the unitary matrix used to reduce the full matrix to tridiagonal form. QSIZ >= N. 
[in]  TLVLS  TLVLS is INTEGER The total number of merging levels in the overall divide and conquer tree. 
[in]  CURLVL  CURLVL is INTEGER The current level in the overall merge routine, 0 <= curlvl <= tlvls. 
[in]  CURPBM  CURPBM is INTEGER The current problem in the current level in the overall merge routine (counting from upper left to lower right). 
[in,out]  D  D is REAL array, dimension (N) On entry, the eigenvalues of the rank1perturbed matrix. On exit, the eigenvalues of the repaired matrix. 
[in,out]  Q  Q is COMPLEX array, dimension (LDQ,N) On entry, the eigenvectors of the rank1perturbed matrix. On exit, the eigenvectors of the repaired tridiagonal matrix. 
[in]  LDQ  LDQ is INTEGER The leading dimension of the array Q. LDQ >= max(1,N). 
[in]  RHO  RHO is REAL Contains the subdiagonal element used to create the rank1 modification. 
[out]  INDXQ  INDXQ 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. 
[out]  IWORK  IWORK is INTEGER array, dimension (4*N) 
[out]  RWORK  RWORK is REAL array, dimension (3*N+2*QSIZ*N) 
[out]  WORK  WORK is COMPLEX array, dimension (QSIZ*N) 
[in,out]  QSTORE  QSTORE is REAL array, dimension (N**2+1) Stores eigenvectors of submatrices encountered during divide and conquer, packed together. QPTR points to beginning of the submatrices. 
[in,out]  QPTR  QPTR 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. 
[in]  PRMPTR  PRMPTR 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. 
[in]  PERM  PERM is INTEGER array, dimension (N lg N) Contains the permutations (from deflation and sorting) to be applied to each eigenblock. 
[in]  GIVPTR  GIVPTR 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. 
[in]  GIVCOL  GIVCOL is INTEGER array, dimension (2, N lg N) Each pair of numbers indicates a pair of columns to take place in a Givens rotation. 
[in]  GIVNUM  GIVNUM is REAL array, dimension (2, N lg N) Each number indicates the S value to be used in the corresponding Givens rotation. 
[out]  INFO  INFO 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 
Definition at line 247 of file claed7.f.