Changing SINK locations creates bug when writing out the RR graph. So, only use this optimization if not writing out.

Author: Nathan Shreve

libs/librrgraph/src/base/rr_graph_utils.cpp

@@ -179,9 +179,6 @@ void set_sink_locs(const RRGraphView& rr_graph, RRGraphBuilder& rr_graph_builder
         auto x_avg = (short)round(std::accumulate(x_coords.begin(), x_coords.end(), 0.f) / (double)x_coords.size());
         auto y_avg = (short)round(std::accumulate(y_coords.begin(), y_coords.end(), 0.f) / (double)y_coords.size());
 
-        VTR_ASSERT(x_avg >= 0);
-        VTR_ASSERT(y_avg >= 0);
-
         RRNodeId node = node_pins.first;
         rr_graph_builder.set_node_coordinates(node, x_avg, y_avg, x_avg, y_avg);
     }

libs/librrgraph/src/base/rr_graph_utils.h

@@ -63,8 +63,15 @@ vtr::vector<RRNodeId, std::vector<RREdgeId>> get_fan_in_list(const RRGraphView&
  * build_rr_graph() sets the location of SINK nodes to span the entire tile they are in. This function sets the location
  * of SINK nodes to be the average coordinate of the IPINs on their cluster block to which they are connected
  *
- * @note
- * This function only changes SINK locations in tiles which have dimensions greater than 1x1
+ * @warning
+ * 1. Do not call this function if the RR graph will be written out.<BR>
+ * 2. If using flat routing, this function must be called before building the intra-cluster RR graph.
+ *
+ * @todo
+ * Either when writing out the RR graph after this function has been called, or reading in an RR graph produced in VPR
+ * after this function was called, an error occurs (many IPINs have no fanins). The reason for this error has not been
+ * determined. However, this is quite a big issue, as choosing to write out the RR graph now significantly increases
+ * runtime!
  */
 void set_sink_locs(const RRGraphView& rr_graph, RRGraphBuilder& rr_graph_builder);
 

terminal_out.txt

@@ -643,7 +643,8 @@ static void build_rr_graph(const t_graph_type graph_type,
                            const int num_directs,
                            int* wire_to_rr_ipin_switch,
                            bool is_flat,
-                           int* Warnings);
+                           int* Warnings,
+                           bool writing_graph_out);
 
 static void build_intra_cluster_rr_graph(const t_graph_type graph_type,
                                          const DeviceGrid& grid,
@@ -714,6 +715,9 @@ void create_rr_graph(const t_graph_type graph_type,
                                                                       router_opts.reorder_rr_graph_nodes_threshold,
                                                                       router_opts.reorder_rr_graph_nodes_seed);
                 }
+
+                if (det_routing_arch->write_rr_graph_filename.empty())
+                    set_sink_locs(device_ctx.rr_graph, mutable_device_ctx.rr_graph_builder);
             }
         } else {
             free_rr_graph();
@@ -736,7 +740,8 @@ void create_rr_graph(const t_graph_type graph_type,
                            directs, num_directs,
                            &det_routing_arch->wire_to_rr_ipin_switch,
                            is_flat,
-                           Warnings);
+                           Warnings,
+                           !det_routing_arch->write_rr_graph_filename.empty());
         }
     }
 
@@ -957,7 +962,8 @@ static void build_rr_graph(const t_graph_type graph_type,
                            const int num_directs,
                            int* wire_to_rr_ipin_switch,
                            bool is_flat,
-                           int* Warnings) {
+                           int* Warnings,
+                           bool writing_graph_out) {
     vtr::ScopedStartFinishTimer timer("Build routing resource graph");
 
     /* Reset warning flag */
@@ -1438,7 +1444,9 @@ static void build_rr_graph(const t_graph_type graph_type,
     }
 
     // Get better locations for SINK nodes
-    set_sink_locs(rr_graph, device_ctx.rr_graph_builder);
+    // Note: this function is also called after load_rr_file() in create_rr_graph()
+    if (!writing_graph_out)
+        set_sink_locs(rr_graph, device_ctx.rr_graph_builder);
 
     // We are done with building the RR Graph. Thus, we can clear the storages only used
     // to build the RR Graph