public class Slaed1
- extends java.lang.Object
Following is the description from the original
Fortran source. For each array argument, the Java
version will include an integer offset parameter, so
the arguments may not match the description exactly.
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* SLAED1 computes the updated eigensystem of a diagonal
* matrix after modification by a rank-one symmetric matrix. This
* routine is used only for the eigenproblem which requires all
* eigenvalues and eigenvectors of a tridiagonal matrix. SLAED7 handles
* the case in which eigenvalues only or eigenvalues and eigenvectors
* of a full symmetric matrix (which was reduced to tridiagonal form)
* are desired.
* T = Q(in) ( D(in) + RHO * Z*Z' ) Q'(in) = Q(out) * D(out) * Q'(out)
* where Z = Q'u, 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
* 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.
* N (input) INTEGER
* The dimension of the symmetric tridiagonal matrix. N >= 0.
* D (input/output) REAL array, dimension (N)
* On entry, the eigenvalues of the rank-1-perturbed matrix.
* On exit, the eigenvalues of the repaired matrix.
* Q (input/output) REAL array, dimension (LDQ,N)
* On entry, the eigenvectors of the rank-1-perturbed matrix.
* On exit, the eigenvectors of the repaired tridiagonal matrix.
* LDQ (input) INTEGER
* The leading dimension of the array Q. LDQ >= max(1,N).
* INDXQ (input/output) INTEGER array, dimension (N)
* On entry, the permutation which separately sorts the two
* subproblems in D into ascending order.
* On exit, the permutation which will reintegrate the
* subproblems back into sorted order,
* i.e. D( INDXQ( I = 1, N ) ) will be in ascending order.
* RHO (input) REAL
* The subdiagonal entry used to create the rank-1 modification.
* CUTPNT (input) INTEGER
* The location of the last eigenvalue in the leading sub-matrix.
* min(1,N) <= CUTPNT <= N/2.
* WORK (workspace) REAL array, dimension (4*N + N**2)
* IWORK (workspace) INTEGER array, dimension (4*N)
* INFO (output) INTEGER
* = 0: successful exit.
* < 0: if INFO = -i, the i-th argument had an illegal value.
* > 0: if INFO = 1, an eigenvalue did not converge
* Further Details
* Based on contributions by
* Jeff Rutter, Computer Science Division, University of California
* at Berkeley, USA
* Modified by Francoise Tisseur, University of Tennessee.
* .. Local Scalars ..
|Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
public static void slaed1(int n,