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.

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.

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

September 2012

  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.