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50 lines
1.3 KiB
50 lines
1.3 KiB
2 years ago
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C Copyright(C) 1999-2020 National Technology & Engineering Solutions
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C of Sandia, LLC (NTESS). Under the terms of Contract DE-NA0003525 with
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C NTESS, the U.S. Government retains certain rights in this software.
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C
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C See packages/seacas/LICENSE for details
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REAL FUNCTION SOLVE (XA, XK, X, XCEN, YCEN, R1, R2)
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C***********************************************************************
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C FUNCTION SOLVE = FINDS A SOLUTION TO THE SPIRAL EQUATION
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C GIVEN AN INTERVAL THAT CONTAINS THE SOLUTION
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C***********************************************************************
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EPS = 1.E-6
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F1 = SPIRAL (XA, XK, X, XCEN, YCEN, R1)
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IF (ABS(F1) .LT. EPS) THEN
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SOLVE = R1
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GO TO 110
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END IF
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F2 = SPIRAL (XA, XK, X, XCEN, YCEN, R2)
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IF (ABS(F2) .LT. EPS) THEN
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SOLVE = R2
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GO TO 110
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END IF
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100 CONTINUE
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IF (ABS(R1 - R2) .LT. EPS) THEN
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SOLVE = (R1 + R2)/2.0
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ELSE
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R3 = (R1 + R2)/2.0
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F3 = SPIRAL (XA, XK, X, XCEN, YCEN, R3)
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IF (ABS(F3) .LT. EPS) THEN
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SOLVE = R3
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GO TO 110
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ELSE IF (F1/F3 .LT. 0.0) THEN
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R2 = R3
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F2 = F3
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ELSE
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R1 = R3
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F1 = F3
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END IF
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GO TO 100
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END IF
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110 CONTINUE
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END
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