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RedHat 9 (Linux i386) - man page for dlasq1 (redhat section l)

DLASQ1(l)					)					DLASQ1(l)

NAME
       DLASQ1  -  compute  the singular values of a real N-by-N bidiagonal matrix with diagonal D
       and off-diagonal E

SYNOPSIS
       SUBROUTINE DLASQ1( N, D, E, WORK, INFO )

	   INTEGER	  INFO, N

	   DOUBLE	  PRECISION D( * ), E( * ), WORK( * )

PURPOSE
       DLASQ1 computes the singular values of a real N-by-N bidiagonal matrix with diagonal D and
       off-diagonal E. The singular values are computed to high relative accuracy, in the absence
       of denormalization, underflow and overflow. The algorithm was first presented in

       "Accurate singular values and differential qd algorithms" by K. V.   Fernando  and  B.  N.
       Parlett, Numer. Math., Vol-67, No. 2, pp. 191-230, 1994,

       and  the  present  implementation is described in "An implementation of the dqds Algorithm
       (Positive Case)", LAPACK Working Note.

ARGUMENTS
       N     (input) INTEGER
	     The number of rows and columns in the matrix. N >= 0.

       D     (input/output) DOUBLE PRECISION array, dimension (N)
	     On entry, D contains the diagonal elements of the bidiagonal  matrix  whose  SVD  is
	     desired. On normal exit, D contains the singular values in decreasing order.

       E     (input/output) DOUBLE PRECISION array, dimension (N)
	     On  entry,  elements  E(1:N-1)  contain  the off-diagonal elements of the bidiagonal
	     matrix whose SVD is desired.  On exit, E is overwritten.

       WORK  (workspace) DOUBLE PRECISION array, dimension (4*N)

       INFO  (output) INTEGER
	     = 0: successful exit
	     < 0: if INFO = -i, the i-th argument had an illegal value
	     > 0: the algorithm failed = 1, a split was marked by a positive value in E = 2, cur-
	     rent  block  of  Z not diagonalized after 30*N iterations (in inner while loop) = 3,
	     termination criterion of outer while loop not met (program created more than N unre-
	     duced blocks)

LAPACK version 3.0			   15 June 2000 				DLASQ1(l)


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