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206 lines
4.8 KiB
206 lines
4.8 KiB
SUBROUTINE DROTMG(DD1,DD2,DX1,DY1,DPARAM)
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* .. Scalar Arguments ..
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DOUBLE PRECISION DD1,DD2,DX1,DY1
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* ..
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* .. Array Arguments ..
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DOUBLE PRECISION DPARAM(5)
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* ..
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*
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* Purpose
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* =======
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*
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* CONSTRUCT THE MODIFIED GIVENS TRANSFORMATION MATRIX H WHICH ZEROS
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* THE SECOND COMPONENT OF THE 2-VECTOR (DSQRT(DD1)*DX1,DSQRT(DD2)*
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* DY2)**T.
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* WITH DPARAM(1)=DFLAG, H HAS ONE OF THE FOLLOWING FORMS..
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*
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* DFLAG=-1.D0 DFLAG=0.D0 DFLAG=1.D0 DFLAG=-2.D0
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*
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* (DH11 DH12) (1.D0 DH12) (DH11 1.D0) (1.D0 0.D0)
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* H=( ) ( ) ( ) ( )
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* (DH21 DH22), (DH21 1.D0), (-1.D0 DH22), (0.D0 1.D0).
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* LOCATIONS 2-4 OF DPARAM CONTAIN DH11, DH21, DH12, AND DH22
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* RESPECTIVELY. (VALUES OF 1.D0, -1.D0, OR 0.D0 IMPLIED BY THE
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* VALUE OF DPARAM(1) ARE NOT STORED IN DPARAM.)
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*
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* THE VALUES OF GAMSQ AND RGAMSQ SET IN THE DATA STATEMENT MAY BE
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* INEXACT. THIS IS OK AS THEY ARE ONLY USED FOR TESTING THE SIZE
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* OF DD1 AND DD2. ALL ACTUAL SCALING OF DATA IS DONE USING GAM.
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*
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*
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* Arguments
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* =========
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*
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* DD1 (input/output) DOUBLE PRECISION
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*
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* DD2 (input/output) DOUBLE PRECISION
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*
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* DX1 (input/output) DOUBLE PRECISION
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*
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* DY1 (input) DOUBLE PRECISION
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*
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* DPARAM (input/output) DOUBLE PRECISION array, dimension 5
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* DPARAM(1)=DFLAG
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* DPARAM(2)=DH11
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* DPARAM(3)=DH21
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* DPARAM(4)=DH12
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* DPARAM(5)=DH22
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*
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* =====================================================================
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*
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* .. Local Scalars ..
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DOUBLE PRECISION DFLAG,DH11,DH12,DH21,DH22,DP1,DP2,DQ1,DQ2,DTEMP,
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+ DU,GAM,GAMSQ,ONE,RGAMSQ,TWO,ZERO
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INTEGER IGO
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* ..
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* .. Intrinsic Functions ..
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INTRINSIC DABS
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* ..
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* .. Data statements ..
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*
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DATA ZERO,ONE,TWO/0.D0,1.D0,2.D0/
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DATA GAM,GAMSQ,RGAMSQ/4096.D0,16777216.D0,5.9604645D-8/
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* ..
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IF (.NOT.DD1.LT.ZERO) GO TO 10
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* GO ZERO-H-D-AND-DX1..
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GO TO 60
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10 CONTINUE
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* CASE-DD1-NONNEGATIVE
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DP2 = DD2*DY1
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IF (.NOT.DP2.EQ.ZERO) GO TO 20
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DFLAG = -TWO
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GO TO 260
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* REGULAR-CASE..
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20 CONTINUE
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DP1 = DD1*DX1
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DQ2 = DP2*DY1
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DQ1 = DP1*DX1
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*
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IF (.NOT.DABS(DQ1).GT.DABS(DQ2)) GO TO 40
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DH21 = -DY1/DX1
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DH12 = DP2/DP1
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*
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DU = ONE - DH12*DH21
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*
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IF (.NOT.DU.LE.ZERO) GO TO 30
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* GO ZERO-H-D-AND-DX1..
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GO TO 60
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30 CONTINUE
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DFLAG = ZERO
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DD1 = DD1/DU
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DD2 = DD2/DU
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DX1 = DX1*DU
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* GO SCALE-CHECK..
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GO TO 100
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40 CONTINUE
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IF (.NOT.DQ2.LT.ZERO) GO TO 50
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* GO ZERO-H-D-AND-DX1..
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GO TO 60
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50 CONTINUE
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DFLAG = ONE
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DH11 = DP1/DP2
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DH22 = DX1/DY1
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DU = ONE + DH11*DH22
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DTEMP = DD2/DU
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DD2 = DD1/DU
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DD1 = DTEMP
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DX1 = DY1*DU
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* GO SCALE-CHECK
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GO TO 100
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* PROCEDURE..ZERO-H-D-AND-DX1..
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60 CONTINUE
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DFLAG = -ONE
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DH11 = ZERO
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DH12 = ZERO
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DH21 = ZERO
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DH22 = ZERO
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*
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DD1 = ZERO
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DD2 = ZERO
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DX1 = ZERO
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* RETURN..
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GO TO 220
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* PROCEDURE..FIX-H..
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70 CONTINUE
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IF (.NOT.DFLAG.GE.ZERO) GO TO 90
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*
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IF (.NOT.DFLAG.EQ.ZERO) GO TO 80
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DH11 = ONE
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DH22 = ONE
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DFLAG = -ONE
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GO TO 90
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80 CONTINUE
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DH21 = -ONE
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DH12 = ONE
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DFLAG = -ONE
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90 CONTINUE
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GO TO IGO(120,150,180,210)
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* PROCEDURE..SCALE-CHECK
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100 CONTINUE
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110 CONTINUE
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IF (.NOT.DD1.LE.RGAMSQ) GO TO 130
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IF (DD1.EQ.ZERO) GO TO 160
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ASSIGN 120 TO IGO
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* FIX-H..
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GO TO 70
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120 CONTINUE
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DD1 = DD1*GAM**2
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DX1 = DX1/GAM
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DH11 = DH11/GAM
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DH12 = DH12/GAM
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GO TO 110
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130 CONTINUE
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140 CONTINUE
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IF (.NOT.DD1.GE.GAMSQ) GO TO 160
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ASSIGN 150 TO IGO
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* FIX-H..
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GO TO 70
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150 CONTINUE
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DD1 = DD1/GAM**2
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DX1 = DX1*GAM
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DH11 = DH11*GAM
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DH12 = DH12*GAM
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GO TO 140
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160 CONTINUE
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170 CONTINUE
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IF (.NOT.DABS(DD2).LE.RGAMSQ) GO TO 190
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IF (DD2.EQ.ZERO) GO TO 220
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ASSIGN 180 TO IGO
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* FIX-H..
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GO TO 70
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180 CONTINUE
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DD2 = DD2*GAM**2
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DH21 = DH21/GAM
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DH22 = DH22/GAM
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GO TO 170
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190 CONTINUE
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200 CONTINUE
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IF (.NOT.DABS(DD2).GE.GAMSQ) GO TO 220
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ASSIGN 210 TO IGO
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* FIX-H..
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GO TO 70
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210 CONTINUE
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DD2 = DD2/GAM**2
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DH21 = DH21*GAM
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DH22 = DH22*GAM
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GO TO 200
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220 CONTINUE
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IF (DFLAG) 250,230,240
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230 CONTINUE
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DPARAM(3) = DH21
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DPARAM(4) = DH12
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GO TO 260
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240 CONTINUE
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DPARAM(2) = DH11
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DPARAM(5) = DH22
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GO TO 260
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250 CONTINUE
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DPARAM(2) = DH11
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DPARAM(3) = DH21
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DPARAM(4) = DH12
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DPARAM(5) = DH22
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260 CONTINUE
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DPARAM(1) = DFLAG
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RETURN
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END
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