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79 lines
2.0 KiB
79 lines
2.0 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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SUBROUTINE GNXKA (MXND, XN, YN, K, NODES, AREA, LXK, NXL, CCW)
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C***********************************************************************
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C SUBROUTINE GNXKA = GENERATES A LIST OF THE FOUR NODES ASSOCIATED WITH
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C ELEMENT K
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C***********************************************************************
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C VARIABLES USED:
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C CCW = .TRUE. IF LIST IS TO BE IN CCW ORDER AND AREA DEFINED
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C (Changed to always put in order and calculate area)
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C***********************************************************************
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REAL XN (MXND), YN (MXND)
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INTEGER NODES(4)
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INTEGER LXK(4, MXND), NXL(2, 3 * MXND)
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LOGICAL CCW
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AREA = 0.0
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DO 10 I = 1, 4
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NODES (I) = 0
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10 CONTINUE
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C... Let line 1 be the base line
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L = LXK(1, K)
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C... Null List
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IF (L .LE. 0) THEN
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RETURN
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ENDIF
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NODES(1) = NXL(1, L)
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NODES(2) = NXL(2, L)
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C... Find other ends of the two sides
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DO 110 I = 2, 4
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L = LXK(I, K)
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M1 = NXL(1, L)
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M2 = NXL(2, L)
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IF (M1 .EQ. NODES(1)) THEN
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NODES(4) = M2
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ELSE IF (M2 .EQ. NODES(1)) THEN
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NODES(4) = M1
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END IF
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IF (M1 .EQ. NODES(2)) THEN
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NODES(3) = M2
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ELSE IF (M2 .EQ. NODES(2)) THEN
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NODES(3) = M1
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END IF
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110 CONTINUE
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C... Compute signed area
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AREA = 0.5 *
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* ((XN(NODES(3)) - XN(NODES(1))) *
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* (YN(NODES(4)) - YN(NODES(2))) -
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& (YN(NODES(3)) - YN(NODES(1))) *
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* (XN(NODES(4)) - XN(NODES(2))))
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IF (AREA .LT. 0.) THEN
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C ... Clockwise case - reverse the order
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NTMP = NODES(2)
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NODES(2) = NODES(4)
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NODES(4) = NTMP
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AREA = -AREA
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ENDIF
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RETURN
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END
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