New debugging function checking that all the gpart<->part and gpart<->spart links are correct.

src/engine.c

@@ -532,27 +532,10 @@ void engine_redistribute(struct engine *e) {
             cells[cid].nodeID);
   }
 
-  /* Verify that the links are correct */
-  for (size_t k = 0; k < nr_gparts; ++k) {
-
-    if (gparts_new[k].id_or_neg_offset <= 0) {
-
-      struct part *part = &parts_new[-gparts_new[k].id_or_neg_offset];
-
-      if (part->gpart != &gparts_new[k]) error("Linking problem !");
-
-      if (gparts_new[k].x[0] != part->x[0] ||
-          gparts_new[k].x[1] != part->x[1] || gparts_new[k].x[2] != part->x[2])
-        error("Linked particles are not at the same position !");
-    }
-  }
-  for (size_t k = 0; k < nr_parts; ++k) {
-
-    if (parts_new[k].gpart != NULL &&
-        parts_new[k].gpart->id_or_neg_offset != -(ptrdiff_t)k) {
-      error("Linking problem !");
-    }
-  }
+/* Verify that the links are correct */
+// part_verify_links(parts_new, gparts_new, sparts_new, nr_parts, nr_gparts,
+// nr_sparts);
+// MATTHIEU
 #endif
 
   /* Set the new part data, free the old. */
@@ -2972,28 +2955,9 @@ void engine_split(struct engine *e, struct partition *initial_partition) {
     part_relink_parts_to_gparts(s->gparts, s->nr_gparts, s->parts);
 
 #ifdef SWIFT_DEBUG_CHECKS
-
   /* Verify that the links are correct */
-  for (size_t k = 0; k < s->nr_gparts; ++k) {
-
-    if (s->gparts[k].id_or_neg_offset <= 0) {
-
-      struct part *part = &s->parts[-s->gparts[k].id_or_neg_offset];
-
-      if (part->gpart != &s->gparts[k]) error("Linking problem !");
-
-      if (s->gparts[k].x[0] != part->x[0] || s->gparts[k].x[1] != part->x[1] ||
-          s->gparts[k].x[2] != part->x[2])
-        error("Linked particles are not at the same position !");
-    }
-  }
-  for (size_t k = 0; k < s->nr_parts; ++k) {
-
-    if (s->parts[k].gpart != NULL &&
-        s->parts[k].gpart->id_or_neg_offset != -(ptrdiff_t)k)
-      error("Linking problem !");
-  }
-
+  part_verify_links(s->parts, s->gparts, s->sparts, s->nr_parts, s->nr_gparts,
+                    s->nr_sparts);
 #endif
 
 #else

src/part.c

@@ -93,6 +93,112 @@ void part_relink_sparts_to_gparts(struct gpart *gparts, size_t N,
   }
 }
 
+/**
+ * @brief Verifies that the #gpart, #part and #spart are correctly linked
+ * together
+ * and that the particle poisitions match.
+ *
+ * This is a debugging function.
+ *
+ * @param parts The #part array.
+ * @param gparts The #gpart array.
+ * @param sparts The #spart array.
+ * @param nr_parts The number of #part in the array.
+ * @param nr_gparts The number of #gpart in the array.
+ * @param nr_sparts The number of #spart in the array.
+ */
+void part_verify_links(struct part *parts, struct gpart *gparts,
+                       struct spart *sparts, size_t nr_parts, size_t nr_gparts,
+                       size_t nr_sparts) {
+
+  for (size_t k = 0; k < nr_gparts; ++k) {
+
+    /* We have a DM particle */
+    if (gparts[k].type == swift_type_dark_matter) {
+
+      /* Check that it's not linked */
+      if (gparts[k].id_or_neg_offset < 0)
+        error("DM gpart particle linked to something !");
+    }
+
+    /* We have a gas particle */
+    else if (gparts[k].type == swift_type_gas) {
+
+      /* Check that it is linked */
+      if (gparts[k].id_or_neg_offset > 0)
+        error("Gas gpart not linked to anything !");
+
+      /* Find its link */
+      const struct part *part = &parts[-gparts[k].id_or_neg_offset];
+
+      /* Check the reverse link */
+      if (part->gpart != &gparts[k]) error("Linking problem !");
+
+      /* Check that the particles are at the same place */
+      if (gparts[k].x[0] != part->x[0] || gparts[k].x[1] != part->x[1] ||
+          gparts[k].x[2] != part->x[2])
+        error("Linked particles are not at the same position !");
+
+    }
+
+    else if (gparts[k].type == swift_type_star) {
+
+      /* Check that it is linked */
+      if (gparts[k].id_or_neg_offset > 0)
+        error("Gas gpart not linked to anything !");
+
+      /* Find its link */
+      const struct spart *spart = &sparts[-gparts[k].id_or_neg_offset];
+
+      /* Check the reverse link */
+      if (spart->gpart != &gparts[k]) error("Linking problem !");
+
+      /* Check that the particles are at the same place */
+      if (gparts[k].x[0] != spart->x[0] || gparts[k].x[1] != spart->x[1] ||
+          gparts[k].x[2] != spart->x[2])
+        error("Linked particles are not at the same position !");
+    }
+  }
+
+  /* Now check that all parts are linked */
+  for (size_t k = 0; k < nr_parts; ++k) {
+
+    /* Ok, there is a link */
+    if (parts[k].gpart != NULL) {
+
+      /* Check the link */
+      if (parts[k].gpart->id_or_neg_offset != -(ptrdiff_t)k) {
+        error("Linking problem !");
+      }
+
+      /* Check that the particles are at the same place */
+      if (parts[k].x[0] != parts[k].gpart->x[0] ||
+          parts[k].x[1] != parts[k].gpart->x[1] ||
+          parts[k].x[2] != parts[k].gpart->x[2])
+        error("Linked particles are not at the same position !");
+    }
+  }
+
+  /* Now check that all sparts are linked */
+  for (size_t k = 0; k < nr_sparts; ++k) {
+
+    /* Ok, there is a link */
+    if (sparts[k].gpart != NULL) {
+
+      /* Check the link */
+      if (sparts[k].gpart->id_or_neg_offset != -(ptrdiff_t)k) {
+        error("Linking problem !");
+
+        /* Check that the particles are at the same place */
+        if (sparts[k].x[0] != sparts[k].gpart->x[0] ||
+            sparts[k].x[1] != sparts[k].gpart->x[1] ||
+            sparts[k].x[2] != sparts[k].gpart->x[2])
+          error("Linked particles are not at the same position !");
+      }
+    }
+  }
+}
+
 #ifdef WITH_MPI
 /* MPI data type for the particle transfers */
 MPI_Datatype part_mpi_type;

src/part.h

@@ -76,6 +76,10 @@ void part_relink_parts_to_gparts(struct gpart *gparts, size_t N,
                                  struct part *parts);
 void part_relink_sparts_to_gparts(struct gpart *gparts, size_t N,
                                   struct spart *sparts);
+void part_verify_links(struct part *parts, struct gpart *gparts,
+                       struct spart *sparts, size_t nr_parts, size_t nr_gparts,
+                       size_t nr_sparts);
+
 #ifdef WITH_MPI
 /* MPI data type for the particle transfers */
 extern MPI_Datatype part_mpi_type;

src/space.c

@@ -738,26 +738,8 @@ void space_rebuild(struct space *s, int verbose) {
 
 #ifdef SWIFT_DEBUG_CHECKS
   /* Verify that the links are correct */
-  for (size_t k = 0; k < nr_gparts; ++k) {
-
-    if (s->gparts[k].id_or_neg_offset < 0) {
-
-      const struct part *part = &s->parts[-s->gparts[k].id_or_neg_offset];
-
-      if (part->gpart != &s->gparts[k]) error("Linking problem !");
-
-      if (s->gparts[k].x[0] != part->x[0] || s->gparts[k].x[1] != part->x[1] ||
-          s->gparts[k].x[2] != part->x[2])
-        error("Linked particles are not at the same position !");
-    }
-  }
-  for (size_t k = 0; k < nr_parts; ++k) {
-
-    if (s->parts[k].gpart != NULL &&
-        s->parts[k].gpart->id_or_neg_offset != -(ptrdiff_t)k) {
-      error("Linking problem !");
-    }
-  }
+  part_verify_links(s->parts, s->gparts, s->sparts, nr_parts, nr_gparts,
+                    nr_sparts);
 #endif
 
   /* Hook the cells up to the parts. */