```      SUBROUTINE SLAS2( F, G, H, SSMIN, SSMAX )
*
*  -- LAPACK auxiliary routine (version 3.1) --
*     Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd..
*     November 2006
*
*     .. Scalar Arguments ..
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.
*
*  ====================================================================
*
*     .. Parameters ..
REAL               ZERO
PARAMETER          ( ZERO = 0.0E0 )
REAL               ONE
PARAMETER          ( ONE = 1.0E0 )
REAL               TWO
PARAMETER          ( TWO = 2.0E0 )
*     ..
*     .. Local Scalars ..
REAL               AS, AT, AU, C, FA, FHMN, FHMX, GA, HA
*     ..
*     .. Intrinsic Functions ..
INTRINSIC          ABS, MAX, MIN, SQRT
*     ..
*     .. Executable Statements ..
*
FA = ABS( F )
GA = ABS( G )
HA = ABS( H )
FHMN = MIN( FA, HA )
FHMX = MAX( FA, HA )
IF( FHMN.EQ.ZERO ) THEN
SSMIN = ZERO
IF( FHMX.EQ.ZERO ) THEN
SSMAX = GA
ELSE
SSMAX = MAX( FHMX, GA )*SQRT( ONE+
\$              ( MIN( FHMX, GA ) / MAX( FHMX, GA ) )**2 )
END IF
ELSE
IF( GA.LT.FHMX ) THEN
AS = ONE + FHMN / FHMX
AT = ( FHMX-FHMN ) / FHMX
AU = ( GA / FHMX )**2
C = TWO / ( SQRT( AS*AS+AU )+SQRT( AT*AT+AU ) )
SSMIN = FHMN*C
SSMAX = FHMX / C
ELSE
AU = FHMX / GA
IF( AU.EQ.ZERO ) THEN
*
*              Avoid possible harmful underflow if exponent range
*              asymmetric (true SSMIN may not underflow even if
*              AU underflows)
*
SSMIN = ( FHMN*FHMX ) / GA
SSMAX = GA
ELSE
AS = ONE + FHMN / FHMX
AT = ( FHMX-FHMN ) / FHMX
C = ONE / ( SQRT( ONE+( AS*AU )**2 )+
\$             SQRT( ONE+( AT*AU )**2 ) )
SSMIN = ( FHMN*C )*AU
SSMIN = SSMIN + SSMIN
SSMAX = GA / ( C+C )
END IF
END IF
END IF
RETURN
*
*     End of SLAS2
*
END

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