Add the potential to the gravity cache.

src/gravity_cache.h

@@ -59,6 +59,9 @@ struct gravity_cache {
   /*! #gpart z acceleration. */
   float *restrict a_z SWIFT_CACHE_ALIGN;
 
+  /*! #gpart potential. */
+  float *restrict pot SWIFT_CACHE_ALIGN;
+
   /*! Is this #gpart active ? */
   int *restrict active SWIFT_CACHE_ALIGN;
 
@@ -85,6 +88,7 @@ static INLINE void gravity_cache_clean(struct gravity_cache *c) {
     free(c->a_x);
     free(c->a_y);
     free(c->a_z);
+    free(c->pot);
     free(c->active);
     free(c->use_mpole);
   }
@@ -120,6 +124,7 @@ static INLINE void gravity_cache_init(struct gravity_cache *c, int count) {
   e += posix_memalign((void **)&c->a_x, SWIFT_CACHE_ALIGNMENT, sizeBytesF);
   e += posix_memalign((void **)&c->a_y, SWIFT_CACHE_ALIGNMENT, sizeBytesF);
   e += posix_memalign((void **)&c->a_z, SWIFT_CACHE_ALIGNMENT, sizeBytesF);
+  e += posix_memalign((void **)&c->pot, SWIFT_CACHE_ALIGNMENT, sizeBytesF);
   e += posix_memalign((void **)&c->active, SWIFT_CACHE_ALIGNMENT, sizeBytesI);
   e +=
       posix_memalign((void **)&c->use_mpole, SWIFT_CACHE_ALIGNMENT, sizeBytesI);
@@ -278,6 +283,7 @@ __attribute__((always_inline)) INLINE void gravity_cache_write_back(
   swift_declare_aligned_ptr(float, a_x, c->a_x, SWIFT_CACHE_ALIGNMENT);
   swift_declare_aligned_ptr(float, a_y, c->a_y, SWIFT_CACHE_ALIGNMENT);
   swift_declare_aligned_ptr(float, a_z, c->a_z, SWIFT_CACHE_ALIGNMENT);
+  swift_declare_aligned_ptr(float, pot, c->pot, SWIFT_CACHE_ALIGNMENT);
   swift_declare_aligned_ptr(int, active, c->active, SWIFT_CACHE_ALIGNMENT);
 
   /* Write stuff back to the particles */
@@ -286,6 +292,7 @@ __attribute__((always_inline)) INLINE void gravity_cache_write_back(
       gparts[i].a_grav[0] += a_x[i];
       gparts[i].a_grav[1] += a_y[i];
       gparts[i].a_grav[2] += a_z[i];
+      gparts[i].potential += pot[i];
     }
   }
 }