Note: this is a BLAS routine and is not in libslatec.a
*DECK SROTMG
SUBROUTINE SROTMG (SD1, SD2, SX1, SY1, SPARAM)
C***BEGIN PROLOGUE SROTMG
C***PURPOSE Construct a modified Givens transformation.
C***LIBRARY SLATEC (BLAS)
C***CATEGORY D1B10
C***TYPE SINGLE PRECISION (SROTMG-S, DROTMG-D)
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***DESCRIPTION
C
C B L A S Subprogram
C Description of Parameters
C
C --Input--
C SD1 single precision scalar
C SD2 single precision scalar
C SX1 single precision scalar
C SY2 single precision scalar
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 SX1 changed to represent the effect of the transformation
C SY2 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
C***REFERENCES C. L. Lawson, R. J. Hanson, D. R. Kincaid and F. T.
C Krogh, Basic linear algebra subprograms for Fortran
C usage, Algorithm No. 539, Transactions on Mathematical
C Software 5, 3 (September 1979), pp. 308-323.
C***ROUTINES CALLED (NONE)
C***REVISION HISTORY (YYMMDD)
C 780301 DATE WRITTEN
C 861211 REVISION DATE from Version 3.2
C 891214 Prologue converted to Version 4.0 format. (BAB)
C 920316 Prologue corrected. (WRB)
C 920501 Reformatted the REFERENCES section. (WRB)
C***END PROLOGUE SROTMG