SUBROUTINE DROTM(N,DX,INCX,DY,INCY,DPARAM) * .. Scalar Arguments .. INTEGER INCX,INCY,N * .. * .. Array Arguments .. DOUBLE PRECISION DPARAM(5),DX(*),DY(*) * .. * * Purpose * ======= * * 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. * * Arguments * ========= * * N (input) INTEGER * number of elements in input vector(s) * * DX (input/output) DOUBLE PRECISION array, dimension N * double precision vector with N elements * * INCX (input) INTEGER * storage spacing between elements of DX * * DY (input/output) DOUBLE PRECISION array, dimension N * double precision vector with N elements * * INCY (input) INTEGER * storage spacing between elements of DY * * DPARAM (input/output) DOUBLE PRECISION array, dimension 5 * DPARAM(1)=DFLAG * DPARAM(2)=DH11 * DPARAM(3)=DH21 * DPARAM(4)=DH12 * DPARAM(5)=DH22 * * ===================================================================== * * .. 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)) GO TO 140 IF (.NOT. (INCX.EQ.INCY.AND.INCX.GT.0)) GO TO 70 * NSTEPS = N*INCX IF (DFLAG.LT.ZERO) THEN GO TO 50 ELSE IF (DFLAG.EQ.ZERO) THEN GO TO 10 ELSE GO TO 30 END IF 10 CONTINUE DH12 = DPARAM(4) DH21 = DPARAM(3) DO 20 I = 1,NSTEPS,INCX W = DX(I) Z = DY(I) DX(I) = W + Z*DH12 DY(I) = W*DH21 + Z 20 CONTINUE GO TO 140 30 CONTINUE DH11 = DPARAM(2) DH22 = DPARAM(5) DO 40 I = 1,NSTEPS,INCX W = DX(I) Z = DY(I) DX(I) = W*DH11 + Z DY(I) = -W + DH22*Z 40 CONTINUE GO TO 140 50 CONTINUE DH11 = DPARAM(2) DH12 = DPARAM(4) DH21 = DPARAM(3) DH22 = DPARAM(5) DO 60 I = 1,NSTEPS,INCX W = DX(I) Z = DY(I) DX(I) = W*DH11 + Z*DH12 DY(I) = W*DH21 + Z*DH22 60 CONTINUE GO TO 140 70 CONTINUE 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 GO TO 120 ELSE IF (DFLAG.EQ.ZERO) THEN GO TO 80 ELSE GO TO 100 END IF 80 CONTINUE DH12 = DPARAM(4) DH21 = DPARAM(3) DO 90 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 90 CONTINUE GO TO 140 100 CONTINUE DH11 = DPARAM(2) DH22 = DPARAM(5) DO 110 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 110 CONTINUE GO TO 140 120 CONTINUE DH11 = DPARAM(2) DH12 = DPARAM(4) DH21 = DPARAM(3) DH22 = DPARAM(5) DO 130 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 130 CONTINUE 140 CONTINUE RETURN END