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SUBROUTINE SROTMG(SD1,SD2,SX1,SY1,SPARAM) |
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* .. Scalar Arguments .. |
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REAL SD1,SD2,SX1,SY1 |
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* .. |
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* .. Array Arguments .. |
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REAL SPARAM(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 (SQRT(SD1)*SX1,SQRT(SD2)* |
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* SY2)**T. |
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* WITH SPARAM(1)=SFLAG, H HAS ONE OF THE FOLLOWING FORMS.. |
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* |
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* SFLAG=-1.E0 SFLAG=0.E0 SFLAG=1.E0 SFLAG=-2.E0 |
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* |
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* (SH11 SH12) (1.E0 SH12) (SH11 1.E0) (1.E0 0.E0) |
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* H=( ) ( ) ( ) ( ) |
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* (SH21 SH22), (SH21 1.E0), (-1.E0 SH22), (0.E0 1.E0). |
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* LOCATIONS 2-4 OF SPARAM CONTAIN SH11,SH21,SH12, AND SH22 |
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* RESPECTIVELY. (VALUES OF 1.E0, -1.E0, OR 0.E0 IMPLIED BY THE |
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* VALUE OF SPARAM(1) ARE NOT STORED IN SPARAM.) |
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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 SD1 AND SD2. 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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* |
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* SD1 (input/output) REAL |
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* |
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* SD2 (input/output) REAL |
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* |
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* SX1 (input/output) REAL |
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* |
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* SY1 (input) REAL |
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* |
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* |
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* SPARAM (input/output) REAL array, dimension 5 |
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* SPARAM(1)=SFLAG |
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* SPARAM(2)=SH11 |
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* SPARAM(3)=SH21 |
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* SPARAM(4)=SH12 |
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* SPARAM(5)=SH22 |
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* |
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* ===================================================================== |
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* |
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* .. Local Scalars .. |
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REAL GAM,GAMSQ,ONE,RGAMSQ,SFLAG,SH11,SH12,SH21,SH22,SP1,SP2,SQ1, |
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+ SQ2,STEMP,SU,TWO,ZERO |
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INTEGER IGO |
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* .. |
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* .. Intrinsic Functions .. |
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INTRINSIC ABS |
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* .. |
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* .. Data statements .. |
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* |
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DATA ZERO,ONE,TWO/0.E0,1.E0,2.E0/ |
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DATA GAM,GAMSQ,RGAMSQ/4096.E0,1.67772E7,5.96046E-8/ |
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* .. |
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|
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IF (.NOT.SD1.LT.ZERO) GO TO 10 |
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* GO ZERO-H-D-AND-SX1.. |
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GO TO 60 |
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10 CONTINUE |
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* CASE-SD1-NONNEGATIVE |
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SP2 = SD2*SY1 |
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IF (.NOT.SP2.EQ.ZERO) GO TO 20 |
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SFLAG = -TWO |
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GO TO 260 |
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* REGULAR-CASE.. |
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20 CONTINUE |
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SP1 = SD1*SX1 |
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SQ2 = SP2*SY1 |
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SQ1 = SP1*SX1 |
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* |
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IF (.NOT.ABS(SQ1).GT.ABS(SQ2)) GO TO 40 |
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SH21 = -SY1/SX1 |
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SH12 = SP2/SP1 |
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* |
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SU = ONE - SH12*SH21 |
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* |
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IF (.NOT.SU.LE.ZERO) GO TO 30 |
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* GO ZERO-H-D-AND-SX1.. |
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GO TO 60 |
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30 CONTINUE |
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SFLAG = ZERO |
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SD1 = SD1/SU |
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SD2 = SD2/SU |
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SX1 = SX1*SU |
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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.SQ2.LT.ZERO) GO TO 50 |
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* GO ZERO-H-D-AND-SX1.. |
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GO TO 60 |
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50 CONTINUE |
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SFLAG = ONE |
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SH11 = SP1/SP2 |
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SH22 = SX1/SY1 |
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SU = ONE + SH11*SH22 |
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STEMP = SD2/SU |
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SD2 = SD1/SU |
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SD1 = STEMP |
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SX1 = SY1*SU |
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* GO SCALE-CHECK |
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GO TO 100 |
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* PROCEDURE..ZERO-H-D-AND-SX1.. |
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60 CONTINUE |
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SFLAG = -ONE |
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SH11 = ZERO |
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SH12 = ZERO |
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SH21 = ZERO |
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SH22 = ZERO |
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* |
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SD1 = ZERO |
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SD2 = ZERO |
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SX1 = 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.SFLAG.GE.ZERO) GO TO 90 |
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* |
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IF (.NOT.SFLAG.EQ.ZERO) GO TO 80 |
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SH11 = ONE |
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SH22 = ONE |
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SFLAG = -ONE |
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GO TO 90 |
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80 CONTINUE |
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SH21 = -ONE |
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SH12 = ONE |
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SFLAG = -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.SD1.LE.RGAMSQ) GO TO 130 |
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IF (SD1.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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SD1 = SD1*GAM**2 |
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SX1 = SX1/GAM |
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SH11 = SH11/GAM |
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SH12 = SH12/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.SD1.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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SD1 = SD1/GAM**2 |
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SX1 = SX1*GAM |
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SH11 = SH11*GAM |
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SH12 = SH12*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.ABS(SD2).LE.RGAMSQ) GO TO 190 |
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IF (SD2.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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SD2 = SD2*GAM**2 |
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SH21 = SH21/GAM |
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SH22 = SH22/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.ABS(SD2).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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SD2 = SD2/GAM**2 |
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SH21 = SH21*GAM |
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SH22 = SH22*GAM |
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GO TO 200 |
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220 CONTINUE |
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IF (SFLAG) 250,230,240 |
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230 CONTINUE |
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SPARAM(3) = SH21 |
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SPARAM(4) = SH12 |
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GO TO 260 |
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240 CONTINUE |
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SPARAM(2) = SH11 |
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SPARAM(5) = SH22 |
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GO TO 260 |
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250 CONTINUE |
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SPARAM(2) = SH11 |
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SPARAM(3) = SH21 |
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SPARAM(4) = SH12 |
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SPARAM(5) = SH22 |
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260 CONTINUE |
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SPARAM(1) = SFLAG |
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RETURN |
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END |