slas2(3F)

NAME
     SLAS2 - compute the singular values of the 2-by-2 matrix  [ F G ]  [ 0 H
     ]

SYNOPSIS
     SUBROUTINE SLAS2( F, G, H, SSMIN, SSMAX )

         REAL          F, G, H, SSMAX, SSMIN

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.


ARGUMENTS
     F       (input) REAL
             The (1,1) element of the 2-by-2 matrix.

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

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

     SSMIN   (output) REAL
             The smaller singular value.

     SSMAX   (output) REAL
             The larger singular value.

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.