| 1 | SUBROUTINE SROTM(N,SX,INCX,SY,INCY,SPARAM) |
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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 | REAL SPARAM(5),SX(1),SY(1) |
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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 | * (SX**T) , WHERE **T INDICATES TRANSPOSE. THE ELEMENTS OF SX ARE IN |
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| 15 | * (DX**T) |
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| 16 | * |
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| 17 | * SX(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 USING LY AND INCY. |
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| 19 | * WITH SPARAM(1)=SFLAG, H HAS ONE OF THE FOLLOWING FORMS.. |
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| 20 | * |
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| 21 | * SFLAG=-1.E0 SFLAG=0.E0 SFLAG=1.E0 SFLAG=-2.E0 |
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| 22 | * |
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| 23 | * (SH11 SH12) (1.E0 SH12) (SH11 1.E0) (1.E0 0.E0) |
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| 24 | * H=( ) ( ) ( ) ( ) |
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| 25 | * (SH21 SH22), (SH21 1.E0), (-1.E0 SH22), (0.E0 1.E0). |
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| 26 | * SEE SROTMG FOR A DESCRIPTION OF DATA STORAGE IN SPARAM. |
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| 27 | * |
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| 28 | * |
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| 29 | * Arguments |
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| 30 | * ========= |
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| 31 | * |
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| 32 | * N (input) INTEGER |
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| 33 | * number of elements in input vector(s) |
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| 34 | * |
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| 35 | * SX (input/output) REAL array, dimension N |
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| 36 | * double precision vector with 5 elements |
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| 37 | * |
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| 38 | * INCX (input) INTEGER |
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| 39 | * storage spacing between elements of SX |
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| 40 | * |
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| 41 | * SY (input/output) REAL array, dimension N |
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| 42 | * double precision vector with N elements |
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| 43 | * |
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| 44 | * INCY (input) INTEGER |
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| 45 | * storage spacing between elements of SY |
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| 46 | * |
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| 47 | * SPARAM (input/output) REAL array, dimension 5 |
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| 48 | * SPARAM(1)=SFLAG |
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| 49 | * SPARAM(2)=SH11 |
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| 50 | * SPARAM(3)=SH21 |
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| 51 | * SPARAM(4)=SH12 |
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| 52 | * SPARAM(5)=SH22 |
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| 53 | * |
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| 54 | * ===================================================================== |
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| 55 | * |
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| 56 | * .. Local Scalars .. |
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| 57 | REAL SFLAG,SH11,SH12,SH21,SH22,TWO,W,Z,ZERO |
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| 58 | INTEGER I,KX,KY,NSTEPS |
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| 59 | * .. |
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| 60 | * .. Data statements .. |
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| 61 | DATA ZERO,TWO/0.E0,2.E0/ |
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| 62 | * .. |
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| 63 | * |
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| 64 | SFLAG = SPARAM(1) |
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| 65 | IF (N.LE.0 .OR. (SFLAG+TWO.EQ.ZERO)) GO TO 140 |
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| 66 | IF (.NOT. (INCX.EQ.INCY.AND.INCX.GT.0)) GO TO 70 |
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| 67 | * |
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| 68 | NSTEPS = N*INCX |
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| 69 | IF (SFLAG) 50,10,30 |
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| 70 | 10 CONTINUE |
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| 71 | SH12 = SPARAM(4) |
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| 72 | SH21 = SPARAM(3) |
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| 73 | DO 20 I = 1,NSTEPS,INCX |
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| 74 | W = SX(I) |
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| 75 | Z = SY(I) |
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| 76 | SX(I) = W + Z*SH12 |
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| 77 | SY(I) = W*SH21 + Z |
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| 78 | 20 CONTINUE |
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| 79 | GO TO 140 |
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| 80 | 30 CONTINUE |
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| 81 | SH11 = SPARAM(2) |
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| 82 | SH22 = SPARAM(5) |
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| 83 | DO 40 I = 1,NSTEPS,INCX |
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| 84 | W = SX(I) |
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| 85 | Z = SY(I) |
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| 86 | SX(I) = W*SH11 + Z |
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| 87 | SY(I) = -W + SH22*Z |
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| 88 | 40 CONTINUE |
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| 89 | GO TO 140 |
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| 90 | 50 CONTINUE |
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| 91 | SH11 = SPARAM(2) |
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| 92 | SH12 = SPARAM(4) |
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| 93 | SH21 = SPARAM(3) |
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| 94 | SH22 = SPARAM(5) |
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| 95 | DO 60 I = 1,NSTEPS,INCX |
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| 96 | W = SX(I) |
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| 97 | Z = SY(I) |
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| 98 | SX(I) = W*SH11 + Z*SH12 |
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| 99 | SY(I) = W*SH21 + Z*SH22 |
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| 100 | 60 CONTINUE |
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| 101 | GO TO 140 |
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| 102 | 70 CONTINUE |
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| 103 | KX = 1 |
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| 104 | KY = 1 |
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| 105 | IF (INCX.LT.0) KX = 1 + (1-N)*INCX |
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| 106 | IF (INCY.LT.0) KY = 1 + (1-N)*INCY |
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| 107 | * |
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| 108 | IF (SFLAG) 120,80,100 |
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| 109 | 80 CONTINUE |
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| 110 | SH12 = SPARAM(4) |
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| 111 | SH21 = SPARAM(3) |
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| 112 | DO 90 I = 1,N |
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| 113 | W = SX(KX) |
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| 114 | Z = SY(KY) |
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| 115 | SX(KX) = W + Z*SH12 |
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| 116 | SY(KY) = W*SH21 + Z |
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| 117 | KX = KX + INCX |
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| 118 | KY = KY + INCY |
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| 119 | 90 CONTINUE |
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| 120 | GO TO 140 |
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| 121 | 100 CONTINUE |
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| 122 | SH11 = SPARAM(2) |
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| 123 | SH22 = SPARAM(5) |
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| 124 | DO 110 I = 1,N |
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| 125 | W = SX(KX) |
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| 126 | Z = SY(KY) |
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| 127 | SX(KX) = W*SH11 + Z |
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| 128 | SY(KY) = -W + SH22*Z |
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| 129 | KX = KX + INCX |
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| 130 | KY = KY + INCY |
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| 131 | 110 CONTINUE |
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| 132 | GO TO 140 |
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| 133 | 120 CONTINUE |
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| 134 | SH11 = SPARAM(2) |
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| 135 | SH12 = SPARAM(4) |
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| 136 | SH21 = SPARAM(3) |
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| 137 | SH22 = SPARAM(5) |
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| 138 | DO 130 I = 1,N |
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| 139 | W = SX(KX) |
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| 140 | Z = SY(KY) |
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| 141 | SX(KX) = W*SH11 + Z*SH12 |
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| 142 | SY(KY) = W*SH21 + Z*SH22 |
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| 143 | KX = KX + INCX |
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| 144 | KY = KY + INCY |
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| 145 | 130 CONTINUE |
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| 146 | 140 CONTINUE |
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| 147 | RETURN |
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| 148 | END |
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