ground/gcs/src/libs/eigen/blas/drotm.f

   1       SUBROUTINE DROTM(N,DX,INCX,DY,INCY,DPARAM)
   2 *     .. Scalar Arguments ..
   3       INTEGER INCX,INCY,N
   4 *     ..
   5 *     .. Array Arguments ..
   6       DOUBLE PRECISION DPARAM(5),DX(*),DY(*)
   7 *     ..
   8 *
   9 *  Purpose
  10 *  =======
  11 *
  12 *     APPLY THE MODIFIED GIVENS TRANSFORMATION, H, TO THE 2 BY N MATRIX
  13 *
  14 *     (DX**T) , WHERE **T INDICATES TRANSPOSE. THE ELEMENTS OF DX ARE IN
  15 *     (DY**T)
  16 *
  17 *     DX(LX+I*INCX), I = 0 TO N-1, WHERE LX = 1 IF INCX .GE. 0, ELSE
  18 *     LX = (-INCX)*N, AND SIMILARLY FOR SY USING LY AND INCY.
  19 *     WITH DPARAM(1)=DFLAG, H HAS ONE OF THE FOLLOWING FORMS..
  20 *
  21 *     DFLAG=-1.D0     DFLAG=0.D0        DFLAG=1.D0     DFLAG=-2.D0
  22 *
  23 *       (DH11  DH12)    (1.D0  DH12)    (DH11  1.D0)    (1.D0  0.D0)
  24 *     H=(          )    (          )    (          )    (          )
  25 *       (DH21  DH22),   (DH21  1.D0),   (-1.D0 DH22),   (0.D0  1.D0).
  26 *     SEE DROTMG FOR A DESCRIPTION OF DATA STORAGE IN DPARAM.
  27 *
  28 *  Arguments
  29 *  =========
  30 *
  31 *  N      (input) INTEGER
  32 *         number of elements in input vector(s)
  33 *
  34 *  DX     (input/output) DOUBLE PRECISION array, dimension N
  35 *         double precision vector with N elements
  36 *
  37 *  INCX   (input) INTEGER
  38 *         storage spacing between elements of DX
  39 *
  40 *  DY     (input/output) DOUBLE PRECISION array, dimension N
  41 *         double precision vector with N elements
  42 *
  43 *  INCY   (input) INTEGER
  44 *         storage spacing between elements of DY
  45 *
  46 *  DPARAM (input/output)  DOUBLE PRECISION array, dimension 5
  47 *     DPARAM(1)=DFLAG
  48 *     DPARAM(2)=DH11
  49 *     DPARAM(3)=DH21
  50 *     DPARAM(4)=DH12
  51 *     DPARAM(5)=DH22
  52 *
  53 *  =====================================================================
  54 *
  55 *     .. Local Scalars ..
  56       DOUBLE PRECISION DFLAG,DH11,DH12,DH21,DH22,TWO,W,Z,ZERO
  57       INTEGER I,KX,KY,NSTEPS
  58 *     ..
  59 *     .. Data statements ..
  60       DATA ZERO,TWO/0.D0,2.D0/
  61 *     ..
  62 *
  63       DFLAG = DPARAM(1)
  64       IF (N.LE.0 .OR. (DFLAG+TWO.EQ.ZERO)) GO TO 140
  65       IF (.NOT. (INCX.EQ.INCY.AND.INCX.GT.0)) GO TO 70
  66 *
  67       NSTEPS = N*INCX
  68       IF (DFLAG) 50,10,30
  69    10 CONTINUE
  70       DH12 = DPARAM(4)
  71       DH21 = DPARAM(3)
  72       DO 20 I = 1,NSTEPS,INCX
  73           W = DX(I)
  74           Z = DY(I)
  75           DX(I) = W + Z*DH12
  76           DY(I) = W*DH21 + Z
  77    20 CONTINUE
  78       GO TO 140
  79    30 CONTINUE
  80       DH11 = DPARAM(2)
  81       DH22 = DPARAM(5)
  82       DO 40 I = 1,NSTEPS,INCX
  83           W = DX(I)
  84           Z = DY(I)
  85           DX(I) = W*DH11 + Z
  86           DY(I) = -W + DH22*Z
  87    40 CONTINUE
  88       GO TO 140
  89    50 CONTINUE
  90       DH11 = DPARAM(2)
  91       DH12 = DPARAM(4)
  92       DH21 = DPARAM(3)
  93       DH22 = DPARAM(5)
  94       DO 60 I = 1,NSTEPS,INCX
  95           W = DX(I)
  96           Z = DY(I)
  97           DX(I) = W*DH11 + Z*DH12
  98           DY(I) = W*DH21 + Z*DH22
  99    60 CONTINUE
 100       GO TO 140
 101    70 CONTINUE
 102       KX = 1
 103       KY = 1
 104       IF (INCX.LT.0) KX = 1 + (1-N)*INCX
 105       IF (INCY.LT.0) KY = 1 + (1-N)*INCY
 106 *
 107       IF (DFLAG) 120,80,100
 108    80 CONTINUE
 109       DH12 = DPARAM(4)
 110       DH21 = DPARAM(3)
 111       DO 90 I = 1,N
 112           W = DX(KX)
 113           Z = DY(KY)
 114           DX(KX) = W + Z*DH12
 115           DY(KY) = W*DH21 + Z
 116           KX = KX + INCX
 117           KY = KY + INCY
 118    90 CONTINUE
 119       GO TO 140
 120   100 CONTINUE
 121       DH11 = DPARAM(2)
 122       DH22 = DPARAM(5)
 123       DO 110 I = 1,N
 124           W = DX(KX)
 125           Z = DY(KY)
 126           DX(KX) = W*DH11 + Z
 127           DY(KY) = -W + DH22*Z
 128           KX = KX + INCX
 129           KY = KY + INCY
 130   110 CONTINUE
 131       GO TO 140
 132   120 CONTINUE
 133       DH11 = DPARAM(2)
 134       DH12 = DPARAM(4)
 135       DH21 = DPARAM(3)
 136       DH22 = DPARAM(5)
 137       DO 130 I = 1,N
 138           W = DX(KX)
 139           Z = DY(KY)
 140           DX(KX) = W*DH11 + Z*DH12
 141           DY(KY) = W*DH21 + Z*DH22
 142           KX = KX + INCX
 143           KY = KY + INCY
 144   130 CONTINUE
 145   140 CONTINUE
 146       RETURN
 147       END