dlas2.f(3)

NAME
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 precision F, double precision G, double precision H, double precision SSMIN, double precision SSMAX)

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.

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 106 of file dlas2.f.

Author

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