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/ALSBC.f | 92 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 92 insertions(+)
 create mode 100644 Utilib/src/ALSBC.f

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

diff --git a/Utilib/src/ALSBC.f b/Utilib/src/ALSBC.f
new file mode 100644
index 0000000..b6684c6
--- /dev/null
+++ b/Utilib/src/ALSBC.f
@@ -0,0 +1,92 @@
+*DECK ALSBC
+      SUBROUTINE ALSBC (N,IS,B,IER,MAX)
+*
+*-----------------------------------------------------------------------
+*
+*Purpose:
+* solution of a system of linear equations using gaussian elimination
+* with partial pivoting. COMPLEX*16 version.
+*
+*Copyright:
+* Copyright (C) 1993 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
+* N       order of the coefficient matrix.
+* IS      number of right hand vectors.
+* B       coefficient matrix augmented with the right hand vectors.
+*         DIMENSION B(MAX,N+IS)
+* MAX     first dimention of matrix B.
+*
+*Parameters: output
+* B       solution vectors, starting at B(1,N+1).
+* IER     error flag. Execution failure if IER.ne.0.
+*
+*-----------------------------------------------------------------------
+*
+      IMPLICIT COMPLEX*16 (A-H,O-Z)
+      DOUBLE PRECISION TEST
+      DIMENSION B(MAX,*)
+      IN=0
+      M=N+IS
+      IER=0
+      IF (N.EQ.1) GO TO 100
+*
+* SEARCH FOR MAXIMUM PIVOT ON COLUMN JCOL.
+      NM1=N-1
+      NP1=N+1
+      DO 60 JCOL=1,NM1
+      TEST=0.0D0
+      DO 10 I=JCOL,N
+      IF (ABS(B(I,JCOL)).LE.TEST) GO TO 10
+      TEST=ABS(B(I,JCOL))
+      IN=I
+10    CONTINUE
+      IF (TEST.EQ.0.0D0) GO TO 120
+*
+* TRIANGULARIZATION.
+      PMX=B(IN,JCOL)
+      B(IN,JCOL)=B(JCOL,JCOL)
+      IP1=JCOL+1
+      DO 50 J=IP1,M
+      PER=B(IN,J)/PMX
+      B(IN,J)=B(JCOL,J)
+      B(JCOL,J)=PER
+      DO 40 I=IP1,N
+      B(I,J)=B(I,J)-B(I,JCOL)*PER
+40    CONTINUE
+50    CONTINUE
+60    CONTINUE
+      PER=B(N,N)
+      DO 70 J=NP1,M
+      B(N,J)=B(N,J)/PER
+70    CONTINUE
+*
+* BACK SUBSTITUTION.
+      DO 95 IN=2,N
+      I=N-IN+1
+      IP1=I+1
+      DO 90 J=NP1,M
+      PER=B(I,J)
+      DO 80 K=IP1,N
+      PER=PER-B(I,K)*B(K,J)
+80    CONTINUE
+      B(I,J)=PER
+90    CONTINUE
+95    CONTINUE
+      RETURN
+*
+100   PER=B(1,1)
+      IF (PER.EQ.(0.0D0,0.0D0)) GO TO 120
+      DO 110 J=2,M
+      B(1,J)=B(1,J)/PER
+110   CONTINUE
+      RETURN
+120   IER=1
+      RETURN
+      END
-- 
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