*> \brief \b DROTM * * =========== DOCUMENTATION =========== * * Online html documentation available at * http://www.netlib.org/lapack/explore-html/ * * Definition: * =========== * * SUBROUTINE DROTM(N,DX,INCX,DY,INCY,DPARAM) * * .. Scalar Arguments .. * INTEGER INCX,INCY,N * .. * .. Array Arguments .. * DOUBLE PRECISION DPARAM(5),DX(*),DY(*) * .. * * *> \par Purpose: * ============= *> *> \verbatim *> *> APPLY THE MODIFIED GIVENS TRANSFORMATION, H, TO THE 2 BY N MATRIX *> *> (DX**T) , WHERE **T INDICATES TRANSPOSE. THE ELEMENTS OF DX ARE IN *> (DY**T) *> *> DX(LX+I*INCX), I = 0 TO N-1, WHERE LX = 1 IF INCX .GE. 0, ELSE *> LX = (-INCX)*N, AND SIMILARLY FOR SY USING LY AND INCY. *> WITH DPARAM(1)=DFLAG, H HAS ONE OF THE FOLLOWING FORMS.. *> *> DFLAG=-1.D0 DFLAG=0.D0 DFLAG=1.D0 DFLAG=-2.D0 *> *> (DH11 DH12) (1.D0 DH12) (DH11 1.D0) (1.D0 0.D0) *> H=( ) ( ) ( ) ( ) *> (DH21 DH22), (DH21 1.D0), (-1.D0 DH22), (0.D0 1.D0). *> SEE DROTMG FOR A DESCRIPTION OF DATA STORAGE IN DPARAM. *> \endverbatim * * Arguments: * ========== * *> \param[in] N *> \verbatim *> N is INTEGER *> number of elements in input vector(s) *> \endverbatim *> *> \param[in,out] DX *> \verbatim *> DX is DOUBLE PRECISION array, dimension ( 1 + ( N - 1 )*abs( INCX ) ) *> \endverbatim *> *> \param[in] INCX *> \verbatim *> INCX is INTEGER *> storage spacing between elements of DX *> \endverbatim *> *> \param[in,out] DY *> \verbatim *> DY is DOUBLE PRECISION array, dimension ( 1 + ( N - 1 )*abs( INCY ) ) *> \endverbatim *> *> \param[in] INCY *> \verbatim *> INCY is INTEGER *> storage spacing between elements of DY *> \endverbatim *> *> \param[in] DPARAM *> \verbatim *> DPARAM is DOUBLE PRECISION array, dimension (5) *> DPARAM(1)=DFLAG *> DPARAM(2)=DH11 *> DPARAM(3)=DH21 *> DPARAM(4)=DH12 *> DPARAM(5)=DH22 *> \endverbatim * * Authors: * ======== * *> \author Univ. of Tennessee *> \author Univ. of California Berkeley *> \author Univ. of Colorado Denver *> \author NAG Ltd. * *> \ingroup double_blas_level1 * * ===================================================================== SUBROUTINE DROTM(N,DX,INCX,DY,INCY,DPARAM) * * -- 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 .. DOUBLE PRECISION DPARAM(5),DX(*),DY(*) * .. * * ===================================================================== * * .. Local Scalars .. DOUBLE PRECISION DFLAG,DH11,DH12,DH21,DH22,TWO,W,Z,ZERO INTEGER I,KX,KY,NSTEPS * .. * .. Data statements .. DATA ZERO,TWO/0.D0,2.D0/ * .. * DFLAG = DPARAM(1) IF (N.LE.0 .OR. (DFLAG+TWO.EQ.ZERO)) RETURN IF (INCX.EQ.INCY.AND.INCX.GT.0) THEN * NSTEPS = N*INCX IF (DFLAG.LT.ZERO) THEN DH11 = DPARAM(2) DH12 = DPARAM(4) DH21 = DPARAM(3) DH22 = DPARAM(5) DO I = 1,NSTEPS,INCX W = DX(I) Z = DY(I) DX(I) = W*DH11 + Z*DH12 DY(I) = W*DH21 + Z*DH22 END DO ELSE IF (DFLAG.EQ.ZERO) THEN DH12 = DPARAM(4) DH21 = DPARAM(3) DO I = 1,NSTEPS,INCX W = DX(I) Z = DY(I) DX(I) = W + Z*DH12 DY(I) = W*DH21 + Z END DO ELSE DH11 = DPARAM(2) DH22 = DPARAM(5) DO I = 1,NSTEPS,INCX W = DX(I) Z = DY(I) DX(I) = W*DH11 + Z DY(I) = -W + DH22*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 (DFLAG.LT.ZERO) THEN DH11 = DPARAM(2) DH12 = DPARAM(4) DH21 = DPARAM(3) DH22 = DPARAM(5) DO I = 1,N W = DX(KX) Z = DY(KY) DX(KX) = W*DH11 + Z*DH12 DY(KY) = W*DH21 + Z*DH22 KX = KX + INCX KY = KY + INCY END DO ELSE IF (DFLAG.EQ.ZERO) THEN DH12 = DPARAM(4) DH21 = DPARAM(3) DO I = 1,N W = DX(KX) Z = DY(KY) DX(KX) = W + Z*DH12 DY(KY) = W*DH21 + Z KX = KX + INCX KY = KY + INCY END DO ELSE DH11 = DPARAM(2) DH22 = DPARAM(5) DO I = 1,N W = DX(KX) Z = DY(KY) DX(KX) = W*DH11 + Z DY(KY) = -W + DH22*Z KX = KX + INCX KY = KY + INCY END DO END IF END IF RETURN * * End of DROTM * END