dlasv2(l) [redhat man page]

DLASV2(l)								 )								 DLASV2(l)

NAME

       DLASV2 - compute the singular value decomposition of a 2-by-2 triangular matrix [ F G ] [ 0 H ]

SYNOPSIS

       SUBROUTINE DLASV2( F, G, H, SSMIN, SSMAX, SNR, CSR, SNL, CSL )

	   DOUBLE	  PRECISION CSL, CSR, F, G, H, SNL, SNR, SSMAX, SSMIN

PURPOSE

       DLASV2  computes the singular value decomposition of a 2-by-2 triangular matrix [ F G ] [ 0 H ]. On return, abs(SSMAX) is the larger singu-
       lar value, abs(SSMIN) is the smaller singular value, and (CSL,SNL) and (CSR,SNR) are the left and right singular  vectors  for  abs(SSMAX),
       giving the decomposition

	  [ CSL  SNL ] [  F   G  ] [ CSR -SNR ]  =  [ SSMAX   0   ]
	  [-SNL  CSL ] [  0   H  ] [ SNR  CSR ]     [  0    SSMIN ].

ARGUMENTS

       F       (input) DOUBLE PRECISION
	       The (1,1) element of the 2-by-2 matrix.

       G       (input) DOUBLE PRECISION
	       The (1,2) element of the 2-by-2 matrix.

       H       (input) DOUBLE PRECISION
	       The (2,2) element of the 2-by-2 matrix.

       SSMIN   (output) DOUBLE PRECISION
	       abs(SSMIN) is the smaller singular value.

       SSMAX   (output) DOUBLE PRECISION
	       abs(SSMAX) is the larger singular value.

       SNL     (output) DOUBLE PRECISION
	       CSL     (output) DOUBLE PRECISION The vector (CSL, SNL) is a unit left singular vector for the singular value abs(SSMAX).

       SNR     (output) DOUBLE PRECISION
	       CSR     (output) DOUBLE PRECISION The vector (CSR, SNR) is a unit right singular vector for the singular value abs(SSMAX).

FURTHER DETAILS

       Any input parameter may be aliased with any output parameter.

       Barring over/underflow and assuming a guard digit in subtraction, all output quantities are correct to within a few units in the last place
       (ulps).

       In IEEE arithmetic, the code works correctly if one matrix element is infinite.

       Overflow will not occur unless the largest singular value itself overflows or is within a few ulps of overflow. (On machines  with  partial
       overflow, like the Cray, overflow may occur if the largest singular value is within a factor of 2 of overflow.)

       Underflow  is  harmless	if  underflow is gradual. Otherwise, results may correspond to a matrix modified by perturbations of size near the
       underflow threshold.

LAPACK version 3.0						   15 June 2000 							 DLASV2(l)

dlasv2.f(3)							      LAPACK							       dlasv2.f(3)

NAME

       dlasv2.f -

SYNOPSIS

   Functions/Subroutines
       subroutine dlasv2 (F, G, H, SSMIN, SSMAX, SNR, CSR, SNL, CSL)
	   DLASV2 computes the singular value decomposition of a 2-by-2 triangular matrix.

Function/Subroutine Documentation
   subroutine dlasv2 (double precisionF, double precisionG, double precisionH, double precisionSSMIN, double precisionSSMAX, double precisionSNR,
       double precisionCSR, double precisionSNL, double precisionCSL)
       DLASV2 computes the singular value decomposition of a 2-by-2 triangular matrix.

       Purpose:

	    DLASV2 computes the singular value decomposition of a 2-by-2
	    triangular matrix
	       [  F   G  ]
	       [  0   H  ].
	    On return, abs(SSMAX) is the larger singular value, abs(SSMIN) is the
	    smaller singular value, and (CSL,SNL) and (CSR,SNR) are the left and
	    right singular vectors for abs(SSMAX), giving the decomposition

	       [ CSL  SNL ] [  F   G  ] [ CSR -SNR ]  =  [ SSMAX   0   ]
	       [-SNL  CSL ] [  0   H  ] [ SNR  CSR ]	 [  0	 SSMIN ].

       Parameters:
	   F

		     F is DOUBLE PRECISION
		     The (1,1) element of the 2-by-2 matrix.

	   G

		     G is DOUBLE PRECISION
		     The (1,2) element of the 2-by-2 matrix.

	   H

		     H is DOUBLE PRECISION
		     The (2,2) element of the 2-by-2 matrix.

	   SSMIN

		     SSMIN is DOUBLE PRECISION
		     abs(SSMIN) is the smaller singular value.

	   SSMAX

		     SSMAX is DOUBLE PRECISION
		     abs(SSMAX) is the larger singular value.

	   SNL

		     SNL is DOUBLE PRECISION

	   CSL

		     CSL is DOUBLE PRECISION
		     The vector (CSL, SNL) is a unit left singular vector for the
		     singular value abs(SSMAX).

	   SNR

		     SNR is DOUBLE PRECISION

	   CSR

		     CSR is DOUBLE PRECISION
		     The vector (CSR, SNR) is a unit right singular vector for the
		     singular value abs(SSMAX).

       Author:
	   Univ. of Tennessee

	   Univ. of California Berkeley

	   Univ. of Colorado Denver

	   NAG Ltd.

       Date:
	   September 2012

       Further Details:

	     Any input parameter may be aliased with any output parameter.

	     Barring over/underflow and assuming a guard digit in subtraction, all
	     output quantities are correct to within a few units in the last
	     place (ulps).

	     In IEEE arithmetic, the code works correctly if one matrix element is
	     infinite.

	     Overflow will not occur unless the largest singular value itself
	     overflows or is within a few ulps of overflow. (On machines with
	     partial overflow, like the Cray, overflow may occur if the largest
	     singular value is within a factor of 2 of overflow.)

	     Underflow is harmless if underflow is gradual. Otherwise, results
	     may correspond to a matrix modified by perturbations of size near
	     the underflow threshold.

       Definition at line 139 of file dlasv2.f.

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

Version 3.4.2							  Tue Sep 25 2012						       dlasv2.f(3)