DLAS2 - compute the singular values of the 2-by-2 matrix [
       F G ] [ 0 H ]


SYNOPSIS

       SUBROUTINE DLAS2( F, G, H, SSMIN, SSMAX )

           DOUBLE        PRECISION F, G, H, SSMAX, SSMIN


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.


ARGUMENTS

       F       (input) DOUBLE PRECISION
               The (1,1) element of the 2-by-2 matrix.

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

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

       SSMIN   (output) DOUBLE PRECISION
               The smaller singular value.

       SSMAX   (output) DOUBLE PRECISION
               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  perturba­
       tions of size near the underflow threshold.


Man(1) output converted with man2html