Cloned SEACAS for EXODUS library with extra build files for internal package management.
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66 lines
1.8 KiB

C Copyright(C) 1999-2020 National Technology & Engineering Solutions
C of Sandia, LLC (NTESS). Under the terms of Contract DE-NA0003525 with
C NTESS, the U.S. Government retains certain rights in this software.
C
C See packages/seacas/LICENSE for details
SUBROUTINE ETHETA (A7, A8, A2, THETA1, THETA2, THETA, ERR)
C***********************************************************************
C SUBROUTINE ETHETA = ITERATIVELY SOLVES THE ELIPTICAL PROBLEM OF
C FINDING AN "A" DISTANCE GIVEN TWO POINTS ON
C THE ELIPSE AND A CENTER POINT
C***********************************************************************
LOGICAL ERR
C START WITH 20 INCREMENTS, EACH PASS INCREMENTS DECREASE TEN FOLD
ANGINC = (THETA2 - THETA1) * .05
ANG = THETA1
F1 = ELIPSE (A7, A8, A2, ANG)
IF (F1 .EQ. 0.0) THEN
THETA = ANG
GO TO 110
END IF
ANG2 = ANG + ANGINC
100 CONTINUE
F2 = ELIPSE (A7, A8, A2, ANG2)
IF (F2 .EQ. 0.0) THEN
THETA = ANG2
ELSE IF (F1*F2 .LT. 0.0) THEN
THETA = ESOLVE (A7, A8, A2, ANG, ANG2)
ELSE
ANG = ANG2
ANG2 = ANG2 + ANGINC
IF (ANG2 .LE. THETA2) GO TO 100
ERR = .TRUE.
GO TO 120
END IF
110 CONTINUE
120 CONTINUE
C FIND THE SECOND ROOT IF THE FIRST ONE HAS BEEN LOCATED
IF(.NOT.ERR)THEN
ANG=THETA+ANGINC
F1 = ELIPSE (A7, A8, A2, ANG)
F2 = ELIPSE (A7, A8, A2, THETA2)
IF (F1 .EQ. 0.0) THEN
THETA = ANG
ELSEIF (F2 .EQ. 0.0) THEN
THETA = THETA2
ELSE IF (F1*F2 .LT. 0.0) THEN
THETA = ESOLVE (A7, A8, A2, ANG, THETA2)
ELSE
GO TO 130
END IF
END IF
130 CONTINUE
RETURN
END