From 7dfcc480ba1e19bd3232349fc733caef94034292 Mon Sep 17 00:00:00 2001
From: stainer_t <thomas.stainer@oecd-nea.org>
Date: Mon, 8 Sep 2025 13:48:49 +0200
Subject: Initial commit from Polytechnique Montreal

---
 Trivac/src/FLDTH2.f | 80 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 80 insertions(+)
 create mode 100755 Trivac/src/FLDTH2.f

(limited to 'Trivac/src/FLDTH2.f')

diff --git a/Trivac/src/FLDTH2.f b/Trivac/src/FLDTH2.f
new file mode 100755
index 0000000..f90b0be
--- /dev/null
+++ b/Trivac/src/FLDTH2.f
@@ -0,0 +1,80 @@
+*DECK FLDTH2
+      SUBROUTINE FLDTH2 (ISPLH,NEL,NUN,EVECT,MAT,VOL,IDL,KN)
+*
+*-----------------------------------------------------------------------
+*
+*Purpose:
+* Calculation of the averaged flux with a linear Lagrangian finite
+* element or mesh corner finite difference method in hexagonal geometry.
+*
+*Copyright:
+* Copyright (C) 2002 Ecole Polytechnique de Montreal
+* This library is free software; you can redistribute it and/or
+* modify it under the terms of the GNU Lesser General Public
+* License as published by the Free Software Foundation; either
+* version 2.1 of the License, or (at your option) any later version
+*
+*Author(s): A. Hebert
+*
+*Parameters: input
+* ISPLH   type of hexagonal mesh-splitting: =1 for complete hexagons;
+*         =2 for triangular mesh-splitting.
+* NEL     total number of finite elements.
+* NUN     total number of unknowns per energy group.
+* EVECT   variational coefficients of the flux. The information is
+*         contained in position EVECT(1) to EVECT(LL4) where LL4 is
+*         the order of the system matrices.
+* MAT     mixture index assigned to each element.
+* VOL     volume of each element.
+* IDL     position of the average flux component associated with each
+*         volume.
+* KN      element-ordered unknown list.
+*
+*Parameters: output
+* EVECT   averaged fluxes. The information is contained in positions
+*         EVECT(IDL(I)).
+*
+*-----------------------------------------------------------------------
+*
+*----
+*  SUBROUTINE ARGUMENTS
+*----
+      INTEGER ISPLH,NEL,NUN,MAT(NEL),IDL(NEL),KN(14*NEL)
+      REAL EVECT(NUN),VOL(NEL)
+*----
+*  LOCAL VARIABLES
+*----
+      REAL TH(14)
+      SAVE TH
+      DATA TH/3*0.055555555556,0.166666666667,6*0.055555555556,
+     1 0.166666666667,3*0.055555555556/
+*
+      NUM1=0
+      IF(ISPLH.EQ.1) THEN
+         SS=1.0/12.0
+         DO 40 K=1,NEL
+         IF(MAT(K).EQ.0) GO TO 40
+         EVECT(IDL(K))=0.0
+         IF(VOL(K).EQ.0.0) GO TO 30
+         DO 20 I=1,12
+         IND1=KN(NUM1+I)
+         IF(IND1.EQ.0) GO TO 20
+         EVECT(IDL(K))=EVECT(IDL(K))+SS*EVECT(IND1)
+   20    CONTINUE
+   30    NUM1=NUM1+12
+   40    CONTINUE
+      ELSE IF(ISPLH.EQ.2) THEN
+         DO 70 K=1,NEL
+         IF(MAT(K).EQ.0) GO TO 70
+         EVECT(IDL(K))=0.0
+         IF(VOL(K).EQ.0.0) GO TO 60
+         DO 50 I=1,14
+         IND1=KN(NUM1+I)
+         IF(IND1.EQ.0) GO TO 50
+         EVECT(IDL(K))=EVECT(IDL(K))+TH(I)*EVECT(IND1)
+   50    CONTINUE
+   60    NUM1=NUM1+14
+   70    CONTINUE
+      ENDIF
+      RETURN
+      END
-- 
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