109 lines
3.2 KiB
Fortran
109 lines
3.2 KiB
Fortran
SUBROUTINE DROTMF (N,DX,INCX,DY,INCY,DPARAM)
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C
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C APPLY THE MODIFIED GIVENS TRANSFORMATION, H, TO THE 2 BY N MATRIX
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C
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C (DX**T) , WHERE **T INDICATES TRANSPOSE. THE ELEMENTS OF DX ARE IN
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C (DY**T)
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C
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C DX(LX+I*INCX), I = 0 TO N-1, WHERE LX = 1 IF INCX .GE. 0, ELSE
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C LX = (-INCX)*N, AND SIMILARLY FOR SY USING LY AND INCY.
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C WITH DPARAM(1)=DFLAG, H HAS ONE OF THE FOLLOWING FORMS..
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C
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C DFLAG=-1.D0 DFLAG=0.D0 DFLAG=1.D0 DFLAG=-2.D0
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C
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C (DH11 DH12) (1.D0 DH12) (DH11 1.D0) (1.D0 0.D0)
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C H=( ) ( ) ( ) ( )
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C (DH21 DH22), (DH21 1.D0), (-1.D0 DH22), (0.D0 1.D0).
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C SEE DROTMG FOR A DESCRIPTION OF DATA STORAGE IN DPARAM.
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C
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DOUBLE PRECISION DFLAG,DH12,DH22,DX,TWO,Z,DH11,DH21,
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1 DPARAM,DY,W,ZERO
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DIMENSION DX(1),DY(1),DPARAM(5)
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DATA ZERO,TWO/0.D0,2.D0/
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C
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DFLAG=DPARAM(1)
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IF(N .LE. 0 .OR.(DFLAG+TWO.EQ.ZERO)) GO TO 140
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IF(.NOT.(INCX.EQ.INCY.AND. INCX .GT.0)) GO TO 70
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C
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NSTEPS=N*INCX
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IF(DFLAG) 50,10,30
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10 CONTINUE
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DH12=DPARAM(4)
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DH21=DPARAM(3)
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DO 20 I=1,NSTEPS,INCX
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W=DX(I)
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Z=DY(I)
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DX(I)=W+Z*DH12
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DY(I)=W*DH21+Z
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20 CONTINUE
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GO TO 140
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30 CONTINUE
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DH11=DPARAM(2)
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DH22=DPARAM(5)
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DO 40 I=1,NSTEPS,INCX
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W=DX(I)
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Z=DY(I)
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DX(I)=W*DH11+Z
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DY(I)=-W+DH22*Z
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40 CONTINUE
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GO TO 140
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50 CONTINUE
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DH11=DPARAM(2)
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DH12=DPARAM(4)
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DH21=DPARAM(3)
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DH22=DPARAM(5)
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DO 60 I=1,NSTEPS,INCX
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W=DX(I)
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Z=DY(I)
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DX(I)=W*DH11+Z*DH12
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DY(I)=W*DH21+Z*DH22
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60 CONTINUE
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GO TO 140
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70 CONTINUE
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KX=1
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KY=1
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IF(INCX .LT. 0) KX=1+(1-N)*INCX
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IF(INCY .LT. 0) KY=1+(1-N)*INCY
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C
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IF(DFLAG)120,80,100
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80 CONTINUE
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DH12=DPARAM(4)
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DH21=DPARAM(3)
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DO 90 I=1,N
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W=DX(KX)
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Z=DY(KY)
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DX(KX)=W+Z*DH12
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DY(KY)=W*DH21+Z
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KX=KX+INCX
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KY=KY+INCY
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90 CONTINUE
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GO TO 140
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100 CONTINUE
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DH11=DPARAM(2)
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DH22=DPARAM(5)
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DO 110 I=1,N
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W=DX(KX)
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Z=DY(KY)
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DX(KX)=W*DH11+Z
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DY(KY)=-W+DH22*Z
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KX=KX+INCX
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KY=KY+INCY
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110 CONTINUE
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GO TO 140
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120 CONTINUE
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DH11=DPARAM(2)
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DH12=DPARAM(4)
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DH21=DPARAM(3)
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DH22=DPARAM(5)
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DO 130 I=1,N
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W=DX(KX)
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Z=DY(KY)
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DX(KX)=W*DH11+Z*DH12
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DY(KY)=W*DH21+Z*DH22
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KX=KX+INCX
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KY=KY+INCY
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130 CONTINUE
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140 CONTINUE
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RETURN
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END
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