| 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) 50,10,30 |
| 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) 120,80,100 |
| 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 |
