[lib][rr_graph] apply comments for rr_graph_storage

Author: amin1377

libs/librrgraph/src/base/rr_graph_storage.cpp

@@ -186,8 +186,8 @@ void t_rr_graph_storage::init_fan_in() {
     node_fan_in_.resize(node_storage_.size(), 0);
     node_fan_in_.shrink_to_fit();
     //Walk the graph and increment fanin on all downstream nodes
-    for(const auto& edge_id : edge_dest_node_.keys()) {
-        node_fan_in_[edge_dest_node_[edge_id]] += 1;
+    for(const auto& [_, dest_node] : edge_dest_node_.pairs()) {
+        node_fan_in_[dest_node] += 1;
     }
 }
 

libs/librrgraph/src/base/rr_graph_storage.h

@@ -705,10 +705,22 @@ class t_rr_graph_storage {
     void set_node_capacity(RRNodeId, short new_capacity);
     void set_node_direction(RRNodeId, Direction new_direction);
 
+    /**
+     * @brief Set the ptc numbers for a node.
+     * @param node The node id
+     * @param ptc_str The ptc numbers string. Note that if tileable RR Graph is used,
+     * multiple ptc numbers can be assigned to node of the type of CHANX or CHANY. If that's the case,
+     * the ptc numbers are separated by commas.
+     */
     void set_node_ptc_nums(RRNodeId node, const std::string& ptc_str);
-    void add_node_tilable_track_num(RRNodeId node, size_t node_offset, short track_id);
 
-    void emplace_back_node_tilable_track_num();
+    /**
+     * @brief Add a track number to a node.
+     * @param node The node id
+     * @param node_offset The offset of the node from the beginning of the node.
+     * @param track_id The track number (ptc number) of the node at the given offset.
+     */
+    void add_node_tilable_track_num(RRNodeId node, size_t node_offset, short track_id);
 
     bool node_contain_multiple_ptc(RRNodeId node) const {
         if (node_tilable_track_nums_.empty()) {