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