[vpr][place][net_cost] fix num_inter_dir_conn corner cases

Author: amin1377

vpr/src/place/net_cost_handler.cpp

@@ -1604,16 +1604,29 @@ double NetCostHandler::get_net_wirelength_from_layer_bb_(ClusterNetId net_id) {
     return ncost;
 }
 
-float NetCostHandler::get_chanz_cost_factor(const t_bb& bounding_box, float place_cost_exp) {
+float NetCostHandler::get_chanz_cost_factor(const t_bb& bounding_box) {
+    float place_cost_exp = placer_opts_.place_cost_exp;
     int x_high = bounding_box.xmax;
     int x_low = bounding_box.xmin;
     int y_high = bounding_box.ymax;
     int y_low = bounding_box.ymin;
 
-    int num_inter_dir_conn = acc_tile_num_inter_die_conn_[x_high][y_high] - \
-                            acc_tile_num_inter_die_conn_[x_low-1][y_high] - \
-                            acc_tile_num_inter_die_conn_[x_high][y_low-1] + \
-                            acc_tile_num_inter_die_conn_[x_low-1][y_low-1];
+    int num_inter_dir_conn;
+
+    if (x_low == 0 && y_low == 0) {
+        num_inter_dir_conn = acc_tile_num_inter_die_conn_[x_high][y_high];
+    } else if (x_low == 0) {
+        num_inter_dir_conn = acc_tile_num_inter_die_conn_[x_high][y_high] - \
+                             acc_tile_num_inter_die_conn_[x_high][y_low-1];
+    } else if (y_low == 0) {
+        num_inter_dir_conn = acc_tile_num_inter_die_conn_[x_high][y_high] - \
+                             acc_tile_num_inter_die_conn_[x_low-1][y_high];
+    } else {
+        num_inter_dir_conn = acc_tile_num_inter_die_conn_[x_high][y_high] - \
+                             acc_tile_num_inter_die_conn_[x_low-1][y_high] - \
+                             acc_tile_num_inter_die_conn_[x_high][y_low-1] + \
+                             acc_tile_num_inter_die_conn_[x_low-1][y_low-1];
+    }
 
     int bb_num_tiles = (x_high - x_low + 1) * (y_high - y_low + 1);
 
@@ -1623,7 +1636,6 @@ float NetCostHandler::get_chanz_cost_factor(const t_bb& bounding_box, float plac
     } else {
         z_cost_factor = bb_num_tiles / static_cast<float>(num_inter_dir_conn);
         z_cost_factor = pow((double)z_cost_factor, (double)place_cost_exp);
-
     }
 
     return z_cost_factor;