From d1587b38e755c4b16c89ee3e33369d04275a59ff Mon Sep 17 00:00:00 2001
From: Matthieu Schaller <schaller@strw.leidenuniv.nl>
Date: Fri, 24 Apr 2020 13:25:20 +0200
Subject: [PATCH] Do not resinitialse the old accelerations to 0 in
 gravity_init()....

---
 src/gravity/MultiSoftening/gravity.h | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/src/gravity/MultiSoftening/gravity.h b/src/gravity/MultiSoftening/gravity.h
index 10b956dc24..001883a1e8 100644
--- a/src/gravity/MultiSoftening/gravity.h
+++ b/src/gravity/MultiSoftening/gravity.h
@@ -160,7 +160,6 @@ __attribute__((always_inline)) INLINE static void gravity_init_gpart(
   gp->a_grav[1] = 0.f;
   gp->a_grav[2] = 0.f;
   gp->potential = 0.f;
-  gp->old_a_grav_norm = 0.f;
 
 #ifdef SWIFT_GRAVITY_FORCE_CHECKS
   gp->potential_PM = 0.f;
@@ -215,6 +214,10 @@ __attribute__((always_inline)) INLINE static void gravity_end_force(
 
   gp->old_a_grav_norm = sqrtf(gp->old_a_grav_norm);
 
+#ifdef SWIFT_DEBUG_CHECKS
+  if (gp->old_a_grav_norm == 0.f) error("Old acceleration is 0!");
+#endif
+
   /* Let's get physical... */
   gp->a_grav[0] *= const_G;
   gp->a_grav[1] *= const_G;
@@ -267,6 +270,7 @@ __attribute__((always_inline)) INLINE static void gravity_first_init_gpart(
     struct gpart* gp, const struct gravity_props* grav_props) {
 
   gp->time_bin = 0;
+  gp->old_a_grav_norm = 0.f;
 
   gravity_init_gpart(gp);
 }
-- 
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