Source module last modified on Thu, 2 Jul 1998, 23:17;
HTML image of Fortran source automatically generated by for2html on Sun, 23 Jun 2002, 15:10.

      SUBROUTINE DROTM (N,DX,INCX,DY,INCY,DPARAM)
#
#     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.
#
      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/
#
      DFLAG=DPARAM(1)
      IF(N <= 0 ||(DFLAG+TWO==ZERO)) GO TO 140
          IF(! (INCX==INCY&& INCX >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 < 0) KX=1+(1-N)*INCX
          IF(INCY < 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