106 lines
3.1 KiB
Fortran
106 lines
3.1 KiB
Fortran
SUBROUTINE SROTMF (N,SX,INCX,SY,INCY,SPARAM)
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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 (SX**T) , WHERE **T INDICATES TRANSPOSE. THE ELEMENTS OF SX ARE IN
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C (DX**T)
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C
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C SX(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 USING LY AND INCY.
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C WITH SPARAM(1)=SFLAG, H HAS ONE OF THE FOLLOWING FORMS..
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C
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C SFLAG=-1.E0 SFLAG=0.E0 SFLAG=1.E0 SFLAG=-2.E0
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C
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C (SH11 SH12) (1.E0 SH12) (SH11 1.E0) (1.E0 0.E0)
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C H=( ) ( ) ( ) ( )
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C (SH21 SH22), (SH21 1.E0), (-1.E0 SH22), (0.E0 1.E0).
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C SEE SROTMG FOR A DESCRIPTION OF DATA STORAGE IN SPARAM.
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C
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DIMENSION SX(1),SY(1),SPARAM(5)
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DATA ZERO,TWO/0.E0,2.E0/
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C
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SFLAG=SPARAM(1)
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IF(N .LE. 0 .OR.(SFLAG+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(SFLAG) 50,10,30
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10 CONTINUE
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SH12=SPARAM(4)
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SH21=SPARAM(3)
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DO 20 I=1,NSTEPS,INCX
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W=SX(I)
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Z=SY(I)
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SX(I)=W+Z*SH12
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SY(I)=W*SH21+Z
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20 CONTINUE
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GO TO 140
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30 CONTINUE
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SH11=SPARAM(2)
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SH22=SPARAM(5)
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DO 40 I=1,NSTEPS,INCX
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W=SX(I)
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Z=SY(I)
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SX(I)=W*SH11+Z
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SY(I)=-W+SH22*Z
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40 CONTINUE
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GO TO 140
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50 CONTINUE
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SH11=SPARAM(2)
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SH12=SPARAM(4)
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SH21=SPARAM(3)
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SH22=SPARAM(5)
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DO 60 I=1,NSTEPS,INCX
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W=SX(I)
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Z=SY(I)
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SX(I)=W*SH11+Z*SH12
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SY(I)=W*SH21+Z*SH22
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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(SFLAG)120,80,100
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80 CONTINUE
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SH12=SPARAM(4)
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SH21=SPARAM(3)
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DO 90 I=1,N
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W=SX(KX)
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Z=SY(KY)
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SX(KX)=W+Z*SH12
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SY(KY)=W*SH21+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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SH11=SPARAM(2)
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SH22=SPARAM(5)
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DO 110 I=1,N
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W=SX(KX)
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Z=SY(KY)
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SX(KX)=W*SH11+Z
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SY(KY)=-W+SH22*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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SH11=SPARAM(2)
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SH12=SPARAM(4)
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SH21=SPARAM(3)
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SH22=SPARAM(5)
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DO 130 I=1,N
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W=SX(KX)
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Z=SY(KY)
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SX(KX)=W*SH11+Z*SH12
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SY(KY)=W*SH21+Z*SH22
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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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