[pack] Fixed the bug where the number of pop limit stops the search after purposing only the candidate found through connectivity and timing. The causes is the limit not reseting after queue is emptied and refilled with transitive or highfanout candidates.

Author: Rongbo Zhang

vpr/src/pack/greedy_candidate_selector.cpp

@@ -126,6 +126,7 @@ ClusterGainStats GreedyCandidateSelector::create_cluster_gain_stats(
     ClusterGainStats cluster_gain_stats;
     cluster_gain_stats.initial_search_for_feasible_blocks = true;
     cluster_gain_stats.num_search_for_feasible_blocks_occured = 0;
+    cluster_gain_stats.num_search_for_feasible_blocks_occurred_limit = packer_opts_.feasible_block_array_size;
     cluster_gain_stats.feasible_blocks.clear();
     cluster_gain_stats.tie_break_high_fanout_net = AtomNetId::INVALID();
     cluster_gain_stats.explore_transitive_fanout = true;
@@ -602,14 +603,26 @@ t_pack_molecule* GreedyCandidateSelector::get_next_candidate_for_cluster(
     t_pack_molecule* best_molecule = nullptr;
     // checking if there are feasible blocks being proposed
     // checking if number of suggestion reached the limit
-    if (cluster_gain_stats.feasible_blocks.size() > 0 && cluster_gain_stats.num_search_for_feasible_blocks_occured < packer_opts_.feasible_block_array_size) {
+    if (cluster_gain_stats.feasible_blocks.size() > 0 && cluster_gain_stats.num_search_for_feasible_blocks_occured < cluster_gain_stats.num_search_for_feasible_blocks_occurred_limit) {
         best_molecule = cluster_gain_stats.feasible_blocks.pop().first;
         if (best_molecule != nullptr) {
             cluster_gain_stats.num_search_for_feasible_blocks_occured++;
             VTR_ASSERT(!cluster_legalizer.is_mol_clustered(best_molecule));
         }
     }
 
+    // If we have no feasible blocks, or we have reached the limit of number of pops,
+    // then we need to clear the feasible blocks list and reset the number of pops.
+    // This ensures that we can continue searching for feasible blocks for the remaining
+    // steps (2.transitive, 3.high fanout, 4.attraction group).
+    if (cluster_gain_stats.feasible_blocks.size() == 0 || 
+        cluster_gain_stats.num_search_for_feasible_blocks_occured >= cluster_gain_stats.num_search_for_feasible_blocks_occurred_limit ||
+        cluster_gain_stats.feasible_blocks.delete_pending_set.size() == cluster_gain_stats.feasible_blocks.content_set.size()
+    ){
+        cluster_gain_stats.feasible_blocks.clear();
+        cluster_gain_stats.num_search_for_feasible_blocks_occured = 0;
+    }
+
     // If we are allowing unrelated clustering and no molecule has been found,
     // get unrelated candidate for cluster.
     if (allow_unrelated_clustering_ && best_molecule == nullptr) {
@@ -1032,22 +1045,6 @@ void GreedyCandidateSelector::update_candidate_selector_finalize_cluster(
     }
 }
 
-template <typename T_key, typename T_sort>
-LazyPopUniquePriorityQueue<T_key, T_sort>::LazyPopUniquePriorityQueue() {
-    // Initialize the priority queue
-    heap.clear();
-    content_set.clear();
-    delete_pending_set.clear();
-}
-
-template <typename T_key, typename T_sort>
-LazyPopUniquePriorityQueue<T_key, T_sort>::~LazyPopUniquePriorityQueue() {
-    // Clear the priority queue
-    heap.clear();
-    content_set.clear();
-    delete_pending_set.clear();
-}
-
 template <typename T_key, typename T_sort>
 void LazyPopUniquePriorityQueue<T_key, T_sort>::push(T_key key, T_sort value){
     // Insert the key and sort value pair into the queue if it is not already present
@@ -1061,6 +1058,7 @@ void LazyPopUniquePriorityQueue<T_key, T_sort>::push(T_key key, T_sort value){
                    LazyPopUniquePriorityQueueCompare());
                    content_set.insert(key);
 }
+
 template <typename T_key, typename T_sort>
 std::pair<T_key,T_sort> LazyPopUniquePriorityQueue<T_key, T_sort>::pop(){
     std::pair<T_key, T_sort> top_pair;
@@ -1085,14 +1083,6 @@ std::pair<T_key,T_sort> LazyPopUniquePriorityQueue<T_key, T_sort>::pop(){
     return top_pair;
 }
 
-template <typename T_key, typename T_sort>
-void LazyPopUniquePriorityQueue<T_key, T_sort>::clear() {
-    // Clear the priority queue
-    heap.clear();
-    content_set.clear();
-    delete_pending_set.clear();
-}
-
 template <typename T_key, typename T_sort>
 void LazyPopUniquePriorityQueue<T_key, T_sort>::remove(T_key key) {
     // If the key is in the priority queue, remove it from the heap and reheapify
@@ -1119,18 +1109,3 @@ void LazyPopUniquePriorityQueue<T_key, T_sort>::remove_at_pop_time(T_key key) {
     } 
 }
 
-template <typename T_key, typename T_sort>
-bool LazyPopUniquePriorityQueue<T_key, T_sort>::empty() {
-    return heap.empty();
-}
-
-template <typename T_key, typename T_sort>
-size_t LazyPopUniquePriorityQueue<T_key, T_sort>::size() {
-    return heap.size();
-}
-
-template <typename T_key, typename T_sort>
-bool LazyPopUniquePriorityQueue<T_key, T_sort>::contains(T_key key) {
-    return content_set.find(key) != content_set.end();
-}
-

vpr/src/pack/greedy_candidate_selector.h

@@ -116,21 +116,29 @@ class LazyPopUniquePriorityQueue {
          *
          *  @return True if the priority queue is empty, false otherwise.
          */
-        bool empty();
+        bool empty(){
+            return heap.empty();
+        }
 
         /**
          * @brief Clears the priority queue and the tracking sets.
          *
          *  @return None
          */
-        void clear();
+        void clear(){
+            heap.clear();
+            content_set.clear();
+            delete_pending_set.clear();
+        }
 
         /**
          * @brief Get the size of the priority queue.
          *
          *  @return The size of the priority queue.
          */
-        size_t size();
+        size_t size(){
+            return heap.size();
+        }
 
         /**
          * @brief Check if the item refered by the key is in the priority queue.
@@ -139,7 +147,9 @@ class LazyPopUniquePriorityQueue {
          *              The key of the item.
          *  @return True if the key is in the priority queue, false otherwise.
          */
-        bool contains(T_key key);
+        bool contains(T_key key){
+            return content_set.find(key) != content_set.end();
+        }
 };
 
 /**
@@ -205,6 +215,9 @@ struct ClusterGainStats {
     /// @brief Indicator for the initial search for feasible blocks.
     bool initial_search_for_feasible_blocks;
 
+    /// @brief Limit for the number of pop.
+    unsigned num_search_for_feasible_blocks_occurred_limit;
+
     /// @brief Counter for the number of pop.
     unsigned num_search_for_feasible_blocks_occured;
 };