From c0224a640c86e74cfdb680b49fd1411842ad64b5 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Villemot?= <sebastien@dynare.org>
Date: Wed, 20 Feb 2019 13:05:04 +0100
Subject: [PATCH] Dynare++: small optimization in unfolded tensor indexing

---
 dynare++/tl/cc/tensor.cc | 14 ++++++--------
 1 file changed, 6 insertions(+), 8 deletions(-)

diff --git a/dynare++/tl/cc/tensor.cc b/dynare++/tl/cc/tensor.cc
index 2c59caea7..778419247 100644
--- a/dynare++/tl/cc/tensor.cc
+++ b/dynare++/tl/cc/tensor.cc
@@ -83,12 +83,11 @@ UTensor::decrement(IntSequence &v, const IntSequence &nvmx)
 int
 UTensor::getOffset(const IntSequence &v, int nv)
 {
-  int pow = 1;
   int res = 0;
-  for (int i = v.size()-1; i >= 0; i--)
+  for (int i = 0; i < v.size(); i++)
     {
-      res += v[i]*pow;
-      pow *= nv;
+      res *= nv;
+      res += v[i];
     }
   return res;
 }
@@ -98,12 +97,11 @@ UTensor::getOffset(const IntSequence &v, int nv)
 int
 UTensor::getOffset(const IntSequence &v, const IntSequence &nvmx)
 {
-  int pow = 1;
   int res = 0;
-  for (int i = v.size()-1; i >= 0; i--)
+  for (int i = 0; i < v.size(); i++)
     {
-      res += v[i]*pow;
-      pow *= nvmx[i];
+      res *= nvmx[i];
+      res += v[i];
     }
   return res;
 }