| Brian Silverman | 72890c2 | 2015-09-19 14:37:37 -0400 | [diff] [blame] | 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 |