From 5ab8ca9aae1aa0a738ab85476bc390d44d22b747 Mon Sep 17 00:00:00 2001
From: Matthieu Schaller <matthieu.schaller@durham.ac.uk>
Date: Sat, 26 Mar 2016 13:56:05 +0000
Subject: [PATCH] Corrected bug in Gadget-2 calculation of div_v

---
 src/hydro/Gadget2/hydro_iact.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/hydro/Gadget2/hydro_iact.h b/src/hydro/Gadget2/hydro_iact.h
index d31b6be383..603bee6209 100644
--- a/src/hydro/Gadget2/hydro_iact.h
+++ b/src/hydro/Gadget2/hydro_iact.h
@@ -93,8 +93,8 @@ __attribute__((always_inline)) INLINE static void runner_iact_density(
   dv[2] = pi->v[2] - pj->v[2];
   const float dvdr = dv[0] * dx[0] + dv[1] * dx[1] + dv[2] * dx[2];
 
-  pi->div_v += faci * dvdr;
-  pj->div_v += facj * dvdr;
+  pi->div_v -= faci * dvdr;
+  pj->div_v -= facj * dvdr;
 
   /* Compute dv cross r */
   curlvr[0] = dv[1] * dx[2] - dv[2] * dx[1];
-- 
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