Merge branch 'zoom_fix_restart' into 'zoom_merge'

Fixing restarting in a zoom run

See merge request !2139

src/zoom_region/zoom_cell.c

@@ -52,6 +52,9 @@ void zoom_find_void_cells(struct space *s, const int verbose) {
   /* Get the cell pointers. */
   struct cell *cells = s->cells_top;
 
+  /* Zero the void cell count. */
+  zoom_props->nr_void_cells = 0;
+
   /* Get the offset and the number of cells we're dealing with. */
   int offset = zoom_props->bkg_cell_offset;
   int ncells = zoom_props->nr_bkg_cells;

src/zoom_region/zoom_init.c

@@ -431,6 +431,13 @@ void zoom_report_cell_properties(const struct space *s) {
 
   struct zoom_region_properties *zoom_props = s->zoom_props;
 
+  /* Compute the number of background cells along each side of the void
+   * region. */
+  int void_cdim[3];
+  for (int i = 0; i < 3; i++) {
+    void_cdim[i] = (int)ceil(s->zoom_props->void_dim[i] * s->iwidth[i]);
+  }
+
   /* Cdims */
   message("%28s = [%d, %d, %d]", "Background cdim", s->cdim[0], s->cdim[1],
           s->cdim[2]);
@@ -439,6 +446,8 @@ void zoom_report_cell_properties(const struct space *s) {
             zoom_props->buffer_cdim[1], zoom_props->buffer_cdim[2]);
   message("%28s = [%d, %d, %d]", "Zoom cdim", zoom_props->cdim[0],
           zoom_props->cdim[1], zoom_props->cdim[2]);
+  message("%28s = [%d, %d, %d]", "Void cdim", void_cdim[0], void_cdim[1],
+          void_cdim[2]);
 
   /* Dimensions */
   message("%28s = [%f, %f, %f]", "Background Dimensions", s->dim[0], s->dim[1],
@@ -449,6 +458,9 @@ void zoom_report_cell_properties(const struct space *s) {
             zoom_props->buffer_dim[2]);
   message("%28s = [%f, %f, %f]", "Zoom Region Dimensions", zoom_props->dim[0],
           zoom_props->dim[1], zoom_props->dim[2]);
+  message("%28s = [%f, %f, %f]", "Void Region Dimensions",
+          s->zoom_props->void_dim[0], s->zoom_props->void_dim[1],
+          s->zoom_props->void_dim[2]);
 
   /* Cell Widths */
   message("%28s = [%f, %f, %f]", "Background Cell Width", s->width[0],
@@ -552,6 +564,12 @@ void zoom_props_init(struct swift_params *params, struct space *s,
  */
 void zoom_region_init(struct space *s, const int verbose) {
 
+  /* Nothing to do if we are restarting, just report geometry and move on. */
+  if (s->e != NULL && s->e->restarting) {
+    if (verbose) zoom_report_cell_properties(s);
+    return;
+  }
+
   /* Update the neighbour distance in case the gravity props have changed. */
   if (s->e != NULL) {
     s->zoom_props->neighbour_distance =