Add check that cell h_max and dx_max make sense

src/debug.c

@@ -193,6 +193,59 @@ int checkSpacehmax(struct space *s) {
   return 0;
 }
 
+/**
+ * @brief Check if the h_max and dx_max values of a cell's hierarchy are
+ * consistent with the particles. Report verbosely if not.
+ *
+ * @param c the top cell of the hierarchy.
+ * @param depth the recursion depth for use in messages. Set to 0 initially.
+ * @result 1 or 0
+ */
+int checkCellhdxmax(const struct cell *c, int *depth) {
+
+  *depth = *depth + 1;
+
+  float h_max = 0.0f;
+  float dx_max = 0.0f;
+  if (!c->split) {
+    const size_t nr_parts = c->count;
+    struct part *parts = c->parts;
+    for (size_t k = 0; k < nr_parts; k++) {
+      h_max = (h_max > parts[k].h) ? h_max : parts[k].h;
+    }
+  } else {
+    for (int k = 0; k < 8; k++)
+      if (c->progeny[k] != NULL) {
+        struct cell *cp = c->progeny[k];
+        checkCellhdxmax(cp, depth);
+        dx_max = max(dx_max, cp->dx_max);
+        h_max = max(h_max, cp->h_max);
+      }
+  }
+
+  /* Check. */
+  int result = 1;
+  if (c->h_max != h_max) {
+    message("%d Inconsistent h_max: cell %f != parts %f", *depth, c->h_max, h_max);
+    message("location: %f %f %f", c->loc[0], c->loc[1], c->loc[2]);
+    result = 0;
+  }
+  if (c->dx_max != dx_max) {
+    message("%d Inconsistent dx_max: %f != %f", *depth, c->dx_max, dx_max);
+    message("location: %f %f %f", c->loc[0], c->loc[1], c->loc[2]);
+    result = 0;
+  }
+
+  /* Check rebuild criterion. */
+  if (h_max > c->dmin) {
+    message("%d Inconsistent c->dmin: %f > %f", *depth, h_max, c->dmin);
+    message("location: %f %f %f", c->loc[0], c->loc[1], c->loc[2]);
+    result = 0;
+  }
+
+  return result;
+}
+
 #ifdef HAVE_METIS
 
 /**

src/debug.h

@@ -32,6 +32,7 @@ void printParticle_single(const struct part *p, const struct xpart *xp);
 void printgParticle_single(struct gpart *gp);
 
 int checkSpacehmax(struct space *s);
+int checkCellhdxmax(const struct cell *c, int *depth);
 
 #ifdef HAVE_METIS
 #include "metis.h"

src/space.c

@@ -346,7 +346,6 @@ void space_regrid(struct space *s, int verbose) {
     if (verbose)
       message("set cell dimensions to [ %i %i %i ].", cdim[0], cdim[1],
               cdim[2]);
-    fflush(stdout);
 
 #ifdef WITH_MPI
     if (oldnodeIDs != NULL) {
@@ -1563,6 +1562,15 @@ void space_split_mapper(void *map_data, int num_cells, void *extra_data) {
     else
       c->owner = 0; /* Ok, there is really nothing on this rank... */
   }
+
+#ifdef SWIFT_DEBUG_CHECKS
+  /* All cells and particles should have consistent h_max values. */
+  for (int ind = 0; ind < num_cells; ind++) {
+    int depth = 0;
+    if (!checkCellhdxmax(&cells_top[ind], &depth))
+      message("    at cell depth %d", depth);
+  }
+#endif
 }
 
 /**