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

---
 Utilib/src/RANDF.f | 65 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 65 insertions(+)
 create mode 100644 Utilib/src/RANDF.f

(limited to 'Utilib/src/RANDF.f')

diff --git a/Utilib/src/RANDF.f b/Utilib/src/RANDF.f
new file mode 100644
index 0000000..9b9e6de
--- /dev/null
+++ b/Utilib/src/RANDF.f
@@ -0,0 +1,65 @@
+*DECK RANDF
+      SUBROUTINE RANDF(ISEED,IFIRST,RAND)
+*
+*-----------------------------------------------------------------------
+*
+*Purpose:
+* This subroutine returns a pseudo-random number for each invocation.
+* It is a FORTRAN 77 adaptation of the "Integer Version 2" minimal
+* standard number generator whose Pascal code appears in reference.
+*
+*Copyright:
+* Copyright (C) 2008 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): R. Chambon
+*
+*Parameters: input
+* ISEED   the seed for the generation of random numbers.
+* IFIRST  set to 1 to indicate that the seed is being generated.
+*                 
+*Parameters: ouput
+* IFIRST  set to 1 to indicate that the seed is being generated.
+* RAND    random number between 0 and 1.
+*
+*Reference:                     
+* Park, Steven K. and Miller, Keith W., "Random Number Generators:
+* Good Ones are Hard to Find", Communications of the ACM, October 1988.
+*                          
+*-----------------------------------------------------------------------
+*
+      IMPLICIT NONE
+*----
+*  SUBROUTINE ARGUMENTS
+*----
+      INTEGER ISEED,IFIRST
+      REAL    RAND
+      DOUBLE PRECISION D1,D2
+*----
+*  LOCAL VARIABLES
+*----
+      INTEGER  MPLIER,MODLUS,MOBYMP,MOMDMP
+      PARAMETER (MPLIER=16807,MODLUS=2147483647,MOBYMP=127773,
+     +           MOMDMP=2836)
+      INTEGER HVLUE, LVLUE, TESTV, NEXTN
+*
+      IF (IFIRST .EQ. 0) IFIRST = 1
+      NEXTN = ISEED
+*
+      HVLUE = NEXTN / MOBYMP
+      LVLUE = MOD(NEXTN, MOBYMP)
+      TESTV = MPLIER*LVLUE - MOMDMP*HVLUE
+      IF (TESTV .GT. 0) THEN
+        NEXTN = TESTV
+      ELSE
+        NEXTN = TESTV + MODLUS
+      ENDIF
+      D1=DBLE(NEXTN)
+      D2=DBLE(MODLUS)
+      RAND=REAL(D1/D2)
+      ISEED= NEXTN
+      RETURN
+      END
-- 
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