| SUBROUTINE DROTMF (N,DX,INCX,DY,INCY,DPARAM) |
| C |
| C APPLY THE MODIFIED GIVENS TRANSFORMATION, H, TO THE 2 BY N MATRIX |
| C |
| C (DX**T) , WHERE **T INDICATES TRANSPOSE. THE ELEMENTS OF DX ARE IN |
| C (DY**T) |
| C |
| C DX(LX+I*INCX), I = 0 TO N-1, WHERE LX = 1 IF INCX .GE. 0, ELSE |
| C LX = (-INCX)*N, AND SIMILARLY FOR SY USING LY AND INCY. |
| C WITH DPARAM(1)=DFLAG, H HAS ONE OF THE FOLLOWING FORMS.. |
| C |
| C DFLAG=-1.D0 DFLAG=0.D0 DFLAG=1.D0 DFLAG=-2.D0 |
| C |
| C (DH11 DH12) (1.D0 DH12) (DH11 1.D0) (1.D0 0.D0) |
| C H=( ) ( ) ( ) ( ) |
| C (DH21 DH22), (DH21 1.D0), (-1.D0 DH22), (0.D0 1.D0). |
| C SEE DROTMG FOR A DESCRIPTION OF DATA STORAGE IN DPARAM. |
| C |
| DOUBLE PRECISION DFLAG,DH12,DH22,DX,TWO,Z,DH11,DH21, |
| 1 DPARAM,DY,W,ZERO |
| DIMENSION DX(1),DY(1),DPARAM(5) |
| DATA ZERO,TWO/0.D0,2.D0/ |
| C |
| 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 |
| C |
| 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 |
| C |
| 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 |
