Added a check to verify that a field tensor has been initialised before use.

src/multipole.h

@@ -96,6 +96,9 @@ struct grav_tensor {
   /* Total number of gpart this field tensor interacted with */
   long long num_interacted;
 
+  /* Last time this tensor was zeroed */
+  integertime_t ti_init;
+
 #endif
 };
 
@@ -232,9 +235,14 @@ INLINE static void gravity_drift(struct gravity_tensors *m, double dt) {
  *
  * @param l The field tensor.
  */
-INLINE static void gravity_field_tensors_init(struct grav_tensor *l) {
+INLINE static void gravity_field_tensors_init(struct grav_tensor *l,
+                                              integertime_t ti_current) {
 
   bzero(l, sizeof(struct grav_tensor));
+
+#ifdef SWIFT_DEBUG_CHECKS
+  l->ti_init = ti_current;
+#endif
 }
 
 /**
@@ -2185,7 +2193,7 @@ INLINE static void gravity_L2L(struct grav_tensor *la,
                                const double pos_a[3], const double pos_b[3]) {
 
   /* Initialise everything to zero */
-  gravity_field_tensors_init(la);
+  gravity_field_tensors_init(la, 0);
 
 #ifdef SWIFT_DEBUG_CHECKS
   if (lb->num_interacted == 0) error("Shifting tensors that did not interact");

src/runner.c

@@ -557,7 +557,7 @@ void runner_do_init_grav(struct runner *r, struct cell *c, int timer) {
   cell_drift_multipole(c, e);
 
   /* Reset the gravity acceleration tensors */
-  gravity_field_tensors_init(&c->multipole->pot);
+  gravity_field_tensors_init(&c->multipole->pot, e->ti_current);
 
   /* Recurse? */
   if (c->split) {

src/runner_doiact_grav.h

@@ -47,6 +47,8 @@ void runner_do_grav_down(struct runner *r, struct cell *c, int timer) {
 
 #ifdef SWIFT_DEBUG_CHECKS
   if (c->ti_old_multipole != e->ti_current) error("c->multipole not drifted.");
+  if (c->multipole->pot.ti_init != e->ti_current)
+    error("c->field tensor not initialised");
 #endif
 
   if (c->split) { /* Node case */
@@ -61,6 +63,8 @@ void runner_do_grav_down(struct runner *r, struct cell *c, int timer) {
 #ifdef SWIFT_DEBUG_CHECKS
         if (cp->ti_old_multipole != e->ti_current)
           error("cp->multipole not drifted.");
+        if (cp->multipole->pot.ti_init != e->ti_current)
+          error("cp->field tensor not initialised");
 #endif
         struct grav_tensor shifted_tensor;
 
@@ -137,8 +141,8 @@ void runner_dopair_grav_mm(const struct runner *r, struct cell *restrict ci,
 
   if (multi_j->M_000 == 0.f) error("Multipole does not seem to have been set.");
 
-  if (ci->ti_old_multipole != e->ti_current)
-    error("ci->multipole not drifted.");
+  if (ci->multipole->pot.ti_init != e->ti_current)
+    error("ci->grav tensor not initialised.");
 #endif
 
   /* Do we need to drift the multipole ? */