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*> \brief \b SROTM
*
* =========== DOCUMENTATION ===========
*
* Online html documentation available at
* http://www.netlib.org/lapack/explore-html/
*
* Definition:
* ===========
*
* SUBROUTINE SROTM(N,SX,INCX,SY,INCY,SPARAM)
*
* .. Scalar Arguments ..
* INTEGER INCX,INCY,N
* ..
* .. Array Arguments ..
* REAL SPARAM(5),SX(*),SY(*)
* ..
*
*
*> \par Purpose:
* =============
*>
*> \verbatim
*>
*> APPLY THE MODIFIED GIVENS TRANSFORMATION, H, TO THE 2 BY N MATRIX
*>
*> (SX**T) , WHERE **T INDICATES TRANSPOSE. THE ELEMENTS OF SX ARE IN
*> (SX**T)
*>
*> SX(LX+I*INCX), I = 0 TO N-1, WHERE LX = 1 IF INCX .GE. 0, ELSE
*> LX = (-INCX)*N, AND SIMILARLY FOR SY USING USING LY AND INCY.
*> WITH SPARAM(1)=SFLAG, H HAS ONE OF THE FOLLOWING FORMS..
*>
*> SFLAG=-1.E0 SFLAG=0.E0 SFLAG=1.E0 SFLAG=-2.E0
*>
*> (SH11 SH12) (1.E0 SH12) (SH11 1.E0) (1.E0 0.E0)
*> H=( ) ( ) ( ) ( )
*> (SH21 SH22), (SH21 1.E0), (-1.E0 SH22), (0.E0 1.E0).
*> SEE SROTMG FOR A DESCRIPTION OF DATA STORAGE IN SPARAM.
*>
*> \endverbatim
*
* Arguments:
* ==========
*
*> \param[in] N
*> \verbatim
*> N is INTEGER
*> number of elements in input vector(s)
*> \endverbatim
*>
*> \param[in,out] SX
*> \verbatim
*> SX is REAL array, dimension N
*> double precision vector with N elements
*> \endverbatim
*>
*> \param[in] INCX
*> \verbatim
*> INCX is INTEGER
*> storage spacing between elements of SX
*> \endverbatim
*>
*> \param[in,out] SY
*> \verbatim
*> SY is REAL array, dimension N
*> double precision vector with N elements
*> \endverbatim
*>
*> \param[in] INCY
*> \verbatim
*> INCY is INTEGER
*> storage spacing between elements of SY
*> \endverbatim
*>
*> \param[in,out] SPARAM
*> \verbatim
*> SPARAM is REAL array, dimension 5
*> SPARAM(1)=SFLAG
*> SPARAM(2)=SH11
*> SPARAM(3)=SH21
*> SPARAM(4)=SH12
*> SPARAM(5)=SH22
*> \endverbatim
*
* Authors:
* ========
*
*> \author Univ. of Tennessee
*> \author Univ. of California Berkeley
*> \author Univ. of Colorado Denver
*> \author NAG Ltd.
*
*> \date December 2016
*
*> \ingroup single_blas_level1
*
* =====================================================================
SUBROUTINE SROTM(N,SX,INCX,SY,INCY,SPARAM)
*
* -- Reference BLAS level1 routine (version 3.7.0) --
* -- Reference BLAS is a software package provided by Univ. of Tennessee, --
* -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
* December 2016
*
* .. Scalar Arguments ..
INTEGER INCX,INCY,N
* ..
* .. Array Arguments ..
REAL SPARAM(5),SX(*),SY(*)
* ..
*
* =====================================================================
*
* .. Local Scalars ..
REAL SFLAG,SH11,SH12,SH21,SH22,TWO,W,Z,ZERO
INTEGER I,KX,KY,NSTEPS
* ..
* .. Data statements ..
DATA ZERO,TWO/0.E0,2.E0/
* ..
*
SFLAG = SPARAM(1)
IF (N.LE.0 .OR. (SFLAG+TWO.EQ.ZERO)) RETURN
IF (INCX.EQ.INCY.AND.INCX.GT.0) THEN
*
NSTEPS = N*INCX
IF (SFLAG.LT.ZERO) THEN
SH11 = SPARAM(2)
SH12 = SPARAM(4)
SH21 = SPARAM(3)
SH22 = SPARAM(5)
DO I = 1,NSTEPS,INCX
W = SX(I)
Z = SY(I)
SX(I) = W*SH11 + Z*SH12
SY(I) = W*SH21 + Z*SH22
END DO
ELSE IF (SFLAG.EQ.ZERO) THEN
SH12 = SPARAM(4)
SH21 = SPARAM(3)
DO I = 1,NSTEPS,INCX
W = SX(I)
Z = SY(I)
SX(I) = W + Z*SH12
SY(I) = W*SH21 + Z
END DO
ELSE
SH11 = SPARAM(2)
SH22 = SPARAM(5)
DO I = 1,NSTEPS,INCX
W = SX(I)
Z = SY(I)
SX(I) = W*SH11 + Z
SY(I) = -W + SH22*Z
END DO
END IF
ELSE
KX = 1
KY = 1
IF (INCX.LT.0) KX = 1 + (1-N)*INCX
IF (INCY.LT.0) KY = 1 + (1-N)*INCY
*
IF (SFLAG.LT.ZERO) THEN
SH11 = SPARAM(2)
SH12 = SPARAM(4)
SH21 = SPARAM(3)
SH22 = SPARAM(5)
DO I = 1,N
W = SX(KX)
Z = SY(KY)
SX(KX) = W*SH11 + Z*SH12
SY(KY) = W*SH21 + Z*SH22
KX = KX + INCX
KY = KY + INCY
END DO
ELSE IF (SFLAG.EQ.ZERO) THEN
SH12 = SPARAM(4)
SH21 = SPARAM(3)
DO I = 1,N
W = SX(KX)
Z = SY(KY)
SX(KX) = W + Z*SH12
SY(KY) = W*SH21 + Z
KX = KX + INCX
KY = KY + INCY
END DO
ELSE
SH11 = SPARAM(2)
SH22 = SPARAM(5)
DO I = 1,N
W = SX(KX)
Z = SY(KY)
SX(KX) = W*SH11 + Z
SY(KY) = -W + SH22*Z
KX = KX + INCX
KY = KY + INCY
END DO
END IF
END IF
RETURN
END
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