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dlasq1.f(3)				      LAPACK				      dlasq1.f(3)

NAME
       dlasq1.f -

SYNOPSIS
   Functions/Subroutines
       subroutine dlasq1 (N, D, E, WORK, INFO)
	   DLASQ1 computes the singular values of a real square bidiagonal matrix. Used by
	   sbdsqr.

Function/Subroutine Documentation
   subroutine dlasq1 (integerN, double precision, dimension( * )D, double precision, dimension( *
       )E, double precision, dimension( * )WORK, integerINFO)
       DLASQ1 computes the singular values of a real square bidiagonal matrix. Used by sbdsqr.

       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.

       Parameters:
	   N

		     N is INTEGER
		   The number of rows and columns in the matrix. N >= 0.

	   D

		     D is 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

		     E is 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

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

	   INFO

		     INFO is 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, current block of Z not diagonalized after 100*N
			     iterations (in inner while loop)  On exit D and E
			     represent a matrix with the same singular values
			     which the calling subroutine could use to finish the
			     computation, or even feed back into DLASQ1
			= 3, termination criterion of outer while loop not met
			     (program created more than N unreduced blocks)

       Author:
	   Univ. of Tennessee

	   Univ. of California Berkeley

	   Univ. of Colorado Denver

	   NAG Ltd.

       Date:
	   September 2012

       Definition at line 109 of file dlasq1.f.

Author
       Generated automatically by Doxygen for LAPACK from the source code.

Version 3.4.2				 Tue Sep 25 2012			      dlasq1.f(3)
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