SRC/slas2.f(3)

NAME
SRC/slas2.f

SYNOPSIS

  Functions/Subroutines
subroutine slas2 (f, g, h, ssmin, ssmax)
SLAS2 computes singular values of a 2-by-2 triangular matrix.

Function/Subroutine Documentation

  subroutine slas2 (real f, real g, real h, real ssmin, real ssmax)

SLAS2 computes singular values of a 2-by-2 triangular matrix.

Purpose:

     SLAS2  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 REAL
              The (1,1) element of the 2-by-2 matrix.

    G

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

    H

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

    SSMIN

              SSMIN is REAL
              The smaller singular value.

    SSMAX

              SSMAX is REAL
              The larger singular value.

Author
    Univ. of Tennessee

    Univ. of California Berkeley

    Univ. of Colorado Denver

    NAG Ltd.

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.
      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 104 of file slas2.f.

Author

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