SUBROUTINE SROTMG(SD1,SD2,SX1,SY1,SPARAM)
C***BEGIN PROLOGUE  SROTMG
C***DATE WRITTEN   780301   (YYMMDD)
C***REVISION DATE  820801   (YYMMDD)
C***CATEGORY NO.  D1B10
C***KEYWORDS  BLAS,LINEAR ALGEBRA,MODIFIED GIVENS ROTATION,VECTOR
C***AUTHOR  LAWSON, C. L., (JPL)
C           HANSON, R. J., (SNLA)
C           KINCAID, D. R., (U. OF TEXAS)
C           KROGH, F. T., (JPL)
C***PURPOSE  Construct s.p. modified Givens transformation
C***DESCRIPTION
C
C                B L A S  Subprogram
C    Description of Parameters
C
C     --Input--
C      SD1  single precision scalar used to define A1 below
C      SD2  single precision scalar used to define A2 below
C      SB1  single precision scalar defining A1 below
C      SB2  single precision scalar defining A2 below
C   SPARAM  S.P. 5-vector. SPARAM(1)=SFLAG defined below.
C           Locations 2-5 contain the rotation matrix.
C
C     --Output--
C     SD1  changed to represent the effect of the transformation
C     SD2  changed to represent the effect of the transformation
C     SB1  changed to represent the effect of the transformation
C     SB2  unchanged
C
C     Construct the modified Givens transformation matrix H which zeros
C     the second component of the 2-vector  (SQRT(SD1)*SX1,SQRT(SD2)*
C     SY2)**T.
C     With SPARAM(1)=SFLAG, H has one of the following forms..
C
C     SFLAG=-1.E0     SFLAG=0.E0        SFLAG=1.E0     SFLAG=-2.E0
C
C       (SH11  SH12)    (1.E0  SH12)    (SH11  1.E0)    (1.E0  0.E0)
C     H=(          )    (          )    (          )    (          )
C       (SH21  SH22),   (SH21  1.E0),   (-1.E0 SH22),   (0.E0  1.E0).
C
C     Locations 2-5 of SPARAM contain SH11,SH21,SH12, and SH22
C     respectively.  (Values of 1.E0, -1.E0, or 0.E0 implied by the
C     value of SPARAM(1) are not stored in SPARAM.)
C***REFERENCES  LAWSON C.L., HANSON R.J., KINCAID D.R., KROGH F.T.,
C                 *BASIC LINEAR ALGEBRA SUBPROGRAMS FOR FORTRAN USAGE*,
C                 ALGORITHM NO. 539, TRANSACTIONS ON MATHEMATICAL
C                 SOFTWARE, VOLUME 5, NUMBER 3, SEPTEMBER 1979, 308-323
C***ROUTINES CALLED  (NONE)
C***END PROLOGUE  SROTMG