| 1 | SUBROUTINE DROTMG(DD1,DD2,DX1,DY1,DPARAM)
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| 2 | * .. Scalar Arguments ..
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| 3 | DOUBLE PRECISION DD1,DD2,DX1,DY1
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| 4 | * ..
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| 5 | * .. Array Arguments ..
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| 6 | DOUBLE PRECISION DPARAM(5)
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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 | * CONSTRUCT THE MODIFIED GIVENS TRANSFORMATION MATRIX H WHICH ZEROS
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| 13 | * THE SECOND COMPONENT OF THE 2-VECTOR (DSQRT(DD1)*DX1,DSQRT(DD2)*
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| 14 | * DY2)**T.
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| 15 | * WITH DPARAM(1)=DFLAG, H HAS ONE OF THE FOLLOWING FORMS..
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| 16 | *
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| 17 | * DFLAG=-1.D0 DFLAG=0.D0 DFLAG=1.D0 DFLAG=-2.D0
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| 18 | *
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| 19 | * (DH11 DH12) (1.D0 DH12) (DH11 1.D0) (1.D0 0.D0)
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| 20 | * H=( ) ( ) ( ) ( )
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| 21 | * (DH21 DH22), (DH21 1.D0), (-1.D0 DH22), (0.D0 1.D0).
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| 22 | * LOCATIONS 2-4 OF DPARAM CONTAIN DH11, DH21, DH12, AND DH22
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| 23 | * RESPECTIVELY. (VALUES OF 1.D0, -1.D0, OR 0.D0 IMPLIED BY THE
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| 24 | * VALUE OF DPARAM(1) ARE NOT STORED IN DPARAM.)
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| 25 | *
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| 26 | * THE VALUES OF GAMSQ AND RGAMSQ SET IN THE DATA STATEMENT MAY BE
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| 27 | * INEXACT. THIS IS OK AS THEY ARE ONLY USED FOR TESTING THE SIZE
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| 28 | * OF DD1 AND DD2. ALL ACTUAL SCALING OF DATA IS DONE USING GAM.
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| 29 | *
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| 30 | *
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| 31 | * Arguments
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| 32 | * =========
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| 33 | *
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| 34 | * DD1 (input/output) DOUBLE PRECISION
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| 35 | *
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| 36 | * DD2 (input/output) DOUBLE PRECISION
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| 37 | *
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| 38 | * DX1 (input/output) DOUBLE PRECISION
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| 39 | *
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| 40 | * DY1 (input) DOUBLE PRECISION
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| 41 | *
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| 42 | * DPARAM (input/output) DOUBLE PRECISION array, dimension 5
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| 43 | * DPARAM(1)=DFLAG
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| 44 | * DPARAM(2)=DH11
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| 45 | * DPARAM(3)=DH21
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| 46 | * DPARAM(4)=DH12
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| 47 | * DPARAM(5)=DH22
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| 48 | *
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| 49 | * =====================================================================
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| 50 | *
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| 51 | * .. Local Scalars ..
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| 52 | DOUBLE PRECISION DFLAG,DH11,DH12,DH21,DH22,DP1,DP2,DQ1,DQ2,DTEMP,
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| 53 | + DU,GAM,GAMSQ,ONE,RGAMSQ,TWO,ZERO
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| 54 | INTEGER IGO
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| 55 | * ..
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| 56 | * .. Intrinsic Functions ..
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| 57 | INTRINSIC DABS
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| 58 | * ..
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| 59 | * .. Data statements ..
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| 60 | *
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| 61 | DATA ZERO,ONE,TWO/0.D0,1.D0,2.D0/
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| 62 | DATA GAM,GAMSQ,RGAMSQ/4096.D0,16777216.D0,5.9604645D-8/
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| 63 | * ..
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| 64 |
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| 65 | IF (.NOT.DD1.LT.ZERO) GO TO 10
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| 66 | * GO ZERO-H-D-AND-DX1..
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| 67 | GO TO 60
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| 68 | 10 CONTINUE
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| 69 | * CASE-DD1-NONNEGATIVE
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| 70 | DP2 = DD2*DY1
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| 71 | IF (.NOT.DP2.EQ.ZERO) GO TO 20
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| 72 | DFLAG = -TWO
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| 73 | GO TO 260
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| 74 | * REGULAR-CASE..
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| 75 | 20 CONTINUE
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| 76 | DP1 = DD1*DX1
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| 77 | DQ2 = DP2*DY1
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| 78 | DQ1 = DP1*DX1
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| 79 | *
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| 80 | IF (.NOT.DABS(DQ1).GT.DABS(DQ2)) GO TO 40
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| 81 | DH21 = -DY1/DX1
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| 82 | DH12 = DP2/DP1
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| 83 | *
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| 84 | DU = ONE - DH12*DH21
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| 85 | *
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| 86 | IF (.NOT.DU.LE.ZERO) GO TO 30
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| 87 | * GO ZERO-H-D-AND-DX1..
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| 88 | GO TO 60
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| 89 | 30 CONTINUE
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| 90 | DFLAG = ZERO
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| 91 | DD1 = DD1/DU
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| 92 | DD2 = DD2/DU
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| 93 | DX1 = DX1*DU
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| 94 | * GO SCALE-CHECK..
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| 95 | GO TO 100
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| 96 | 40 CONTINUE
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| 97 | IF (.NOT.DQ2.LT.ZERO) GO TO 50
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| 98 | * GO ZERO-H-D-AND-DX1..
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| 99 | GO TO 60
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| 100 | 50 CONTINUE
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| 101 | DFLAG = ONE
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| 102 | DH11 = DP1/DP2
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| 103 | DH22 = DX1/DY1
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| 104 | DU = ONE + DH11*DH22
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| 105 | DTEMP = DD2/DU
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| 106 | DD2 = DD1/DU
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| 107 | DD1 = DTEMP
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| 108 | DX1 = DY1*DU
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| 109 | * GO SCALE-CHECK
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| 110 | GO TO 100
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| 111 | * PROCEDURE..ZERO-H-D-AND-DX1..
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| 112 | 60 CONTINUE
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| 113 | DFLAG = -ONE
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| 114 | DH11 = ZERO
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| 115 | DH12 = ZERO
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| 116 | DH21 = ZERO
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| 117 | DH22 = ZERO
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| 118 | *
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| 119 | DD1 = ZERO
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| 120 | DD2 = ZERO
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| 121 | DX1 = ZERO
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| 122 | * RETURN..
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| 123 | GO TO 220
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| 124 | * PROCEDURE..FIX-H..
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| 125 | 70 CONTINUE
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| 126 | IF (.NOT.DFLAG.GE.ZERO) GO TO 90
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| 127 | *
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| 128 | IF (.NOT.DFLAG.EQ.ZERO) GO TO 80
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| 129 | DH11 = ONE
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| 130 | DH22 = ONE
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| 131 | DFLAG = -ONE
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| 132 | GO TO 90
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| 133 | 80 CONTINUE
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| 134 | DH21 = -ONE
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| 135 | DH12 = ONE
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| 136 | DFLAG = -ONE
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| 137 | 90 CONTINUE
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| 138 | GO TO IGO(120,150,180,210)
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| 139 | * PROCEDURE..SCALE-CHECK
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| 140 | 100 CONTINUE
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| 141 | 110 CONTINUE
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| 142 | IF (.NOT.DD1.LE.RGAMSQ) GO TO 130
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| 143 | IF (DD1.EQ.ZERO) GO TO 160
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| 144 | ASSIGN 120 TO IGO
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| 145 | * FIX-H..
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| 146 | GO TO 70
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| 147 | 120 CONTINUE
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| 148 | DD1 = DD1*GAM**2
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| 149 | DX1 = DX1/GAM
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| 150 | DH11 = DH11/GAM
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| 151 | DH12 = DH12/GAM
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| 152 | GO TO 110
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| 153 | 130 CONTINUE
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| 154 | 140 CONTINUE
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| 155 | IF (.NOT.DD1.GE.GAMSQ) GO TO 160
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| 156 | ASSIGN 150 TO IGO
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| 157 | * FIX-H..
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| 158 | GO TO 70
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| 159 | 150 CONTINUE
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| 160 | DD1 = DD1/GAM**2
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| 161 | DX1 = DX1*GAM
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| 162 | DH11 = DH11*GAM
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| 163 | DH12 = DH12*GAM
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| 164 | GO TO 140
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| 165 | 160 CONTINUE
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| 166 | 170 CONTINUE
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| 167 | IF (.NOT.DABS(DD2).LE.RGAMSQ) GO TO 190
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| 168 | IF (DD2.EQ.ZERO) GO TO 220
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| 169 | ASSIGN 180 TO IGO
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| 170 | * FIX-H..
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| 171 | GO TO 70
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| 172 | 180 CONTINUE
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| 173 | DD2 = DD2*GAM**2
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| 174 | DH21 = DH21/GAM
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| 175 | DH22 = DH22/GAM
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| 176 | GO TO 170
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| 177 | 190 CONTINUE
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| 178 | 200 CONTINUE
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| 179 | IF (.NOT.DABS(DD2).GE.GAMSQ) GO TO 220
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| 180 | ASSIGN 210 TO IGO
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| 181 | * FIX-H..
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| 182 | GO TO 70
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| 183 | 210 CONTINUE
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| 184 | DD2 = DD2/GAM**2
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| 185 | DH21 = DH21*GAM
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| 186 | DH22 = DH22*GAM
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| 187 | GO TO 200
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| 188 | 220 CONTINUE
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| 189 | IF (DFLAG) 250,230,240
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| 190 | 230 CONTINUE
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| 191 | DPARAM(3) = DH21
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| 192 | DPARAM(4) = DH12
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| 193 | GO TO 260
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| 194 | 240 CONTINUE
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| 195 | DPARAM(2) = DH11
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| 196 | DPARAM(5) = DH22
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| 197 | GO TO 260
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| 198 | 250 CONTINUE
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| 199 | DPARAM(2) = DH11
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| 200 | DPARAM(3) = DH21
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| 201 | DPARAM(4) = DH12
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| 202 | DPARAM(5) = DH22
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| 203 | 260 CONTINUE
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| 204 | DPARAM(1) = DFLAG
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| 205 | RETURN
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| 206 | END
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