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/DDOT.f | 76 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 76 insertions(+)
 create mode 100644 Utilib/src/DDOT.f

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

diff --git a/Utilib/src/DDOT.f b/Utilib/src/DDOT.f
new file mode 100644
index 0000000..7d6de16
--- /dev/null
+++ b/Utilib/src/DDOT.f
@@ -0,0 +1,76 @@
+*DECK DDOT
+      DOUBLE PRECISION FUNCTION DDOT(N,SX,INCX,SY,INCY)
+*
+*-----------------------------------------------------------------------
+*
+*Purpose:
+* forms the dot product of two vectors. Uses unrolled loops for
+* increments equal to one.
+*
+*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): Jack Dongarra, linpack, 3/11/78.
+*
+*Parameters: input
+* N       number of components in the vectors.
+* SX      first vector.
+* INCX    increment in first vector.
+* SY      second vector.
+* INCY    increment in second vector.
+*
+*Parameters: output
+* DDOT    dot product.
+*
+*-----------------------------------------------------------------------
+*
+*----
+*  SUBROUTINE ARGUMENTS
+*----
+      INTEGER N,INCX,INCY
+      DOUBLE PRECISION SX(N*INCX),SY(N*INCY)
+*----
+*  LOCAL VARIABLES
+*----
+      INTEGER I,IX,IY,M,MP1
+      DOUBLE PRECISION DTEMP
+*
+      DTEMP = 0.0D0
+      DDOT = 0.0D0
+      IF(N.LE.0)RETURN
+      IF(INCX.EQ.1.AND.INCY.EQ.1)GO TO 20
+*----
+*  CODE FOR UNEQUAL INCREMENTS OR EQUAL INCREMENTS NOT EQUAL TO 1.
+*----
+      IX = 1
+      IY = 1
+      IF(INCX.LT.0)IX = (-N+1)*INCX + 1
+      IF(INCY.LT.0)IY = (-N+1)*INCY + 1
+      DO 10 I = 1,N
+        DTEMP = DTEMP + SX(IX)*SY(IY)
+        IX = IX + INCX
+        IY = IY + INCY
+   10 CONTINUE
+      DDOT = DTEMP
+      RETURN
+*----
+*   CODE FOR BOTH INCREMENTS EQUAL TO 1. CLEAN-UP LOOP.
+*----
+   20 M = MOD(N,5)
+      IF( M .EQ. 0 ) GO TO 40
+      DO 30 I = 1,M
+        DTEMP = DTEMP + SX(I)*SY(I)
+   30 CONTINUE
+      IF( N .LT. 5 ) GO TO 60
+   40 MP1 = M + 1
+      DO 50 I = MP1,N,5
+        DTEMP = DTEMP + SX(I)*SY(I) + SX(I + 1)*SY(I + 1) +
+     *   SX(I + 2)*SY(I + 2) + SX(I + 3)*SY(I + 3) + SX(I + 4)*SY(I + 4)
+   50 CONTINUE
+   60 DDOT = DTEMP
+      RETURN
+      END
-- 
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