dlas2.f man page

dlas2.f —

Synopsis

Functions/Subroutines

subroutine dlas2 (F, G, H, SSMIN, SSMAX)
DLAS2 computes singular values of a 2-by-2 triangular matrix.

Function/Subroutine Documentation

subroutine dlas2 (double precisionF, double precisionG, double precisionH, double precisionSSMIN, double precisionSSMAX)

DLAS2 computes singular values of a 2-by-2 triangular matrix.

Purpose:

DLAS2  computes the singular values of the 2-by-2 matrix
   [  F   G  ]
   [  0   H  ].
On return, SSMIN is the smaller singular value and SSMAX is the
larger singular value.

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
The smaller singular value.

SSMAX

SSMAX is DOUBLE PRECISION
The larger singular value.

Author:

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

Date:

September 2012

Further Details:

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

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 108 of file dlas2.f.

Author

Generated automatically by Doxygen for LAPACK from the source code.

Referenced By

dlas2(3) is an alias of dlas2.f(3).

Sat Nov 16 2013 Version 3.4.2 LAPACK