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 precisionF, double precisionG, double precisionH, double
       precisionSSMIN, double precisionSSMAX)
       DLAS2 computes singular values of a 2-by-2 triangular matrix.

       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.

       Date:
           September 2012

       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 108 of file dlas2.f.

Author

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