*> \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 ( 1 + ( N - 1 )*abs( INCX ) ) *> \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 ( 1 + ( N - 1 )*abs( INCY ) ) *> \endverbatim *> *> \param[in] INCY *> \verbatim *> INCY is INTEGER *> storage spacing between elements of SY *> \endverbatim *> *> \param[in] 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. * *> \ingroup single_blas_level1 * * ===================================================================== SUBROUTINE SROTM(N,SX,INCX,SY,INCY,SPARAM) * * -- Reference BLAS level1 routine -- * -- Reference BLAS is a software package provided by Univ. of Tennessee, -- * -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..-- * * .. 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 of SROTM * END