[Packer] Clean Up Clustering Algorithm

Cleaned up the overall clustering algorithm in the greedy clusterer
class. This change is non-functional, the control flow was rearanged and
inlined / outlined to make the overall clustering algorithm more clear.

More needs to be done to abstract timing and the gain calculation.

Author: AlexandreSinger

vpr/src/base/SetupVPR.cpp

@@ -552,7 +552,6 @@ void SetupPackerOpts(const t_options& Options,
 
     //TODO: document?
     PackerOpts->global_clocks = true;       /* DEFAULT */
-    PackerOpts->hill_climbing_flag = false; /* DEFAULT */
 
     PackerOpts->allow_unrelated_clustering = Options.allow_unrelated_clustering;
     PackerOpts->connection_driven = Options.connection_driven_clustering;

vpr/src/base/ShowSetup.cpp

@@ -706,7 +706,6 @@ static void ShowPackerOpts(const t_packer_opts& PackerOpts) {
     }
     VTR_LOG("PackerOpts.connection_driven: %s", (PackerOpts.connection_driven ? "true\n" : "false\n"));
     VTR_LOG("PackerOpts.global_clocks: %s", (PackerOpts.global_clocks ? "true\n" : "false\n"));
-    VTR_LOG("PackerOpts.hill_climbing_flag: %s", (PackerOpts.hill_climbing_flag ? "true\n" : "false\n"));
     VTR_LOG("PackerOpts.inter_cluster_net_delay: %f\n", PackerOpts.inter_cluster_net_delay);
     VTR_LOG("PackerOpts.timing_driven: %s", (PackerOpts.timing_driven ? "true\n" : "false\n"));
     VTR_LOG("PackerOpts.target_external_pin_util: %s", vtr::join(PackerOpts.target_external_pin_util, " ").c_str());

vpr/src/base/vpr_types.h

@@ -790,7 +790,6 @@ struct t_packer_opts {
     std::string sdc_file_name;
     std::string output_file;
     bool global_clocks;
-    bool hill_climbing_flag;
     bool timing_driven;
     enum e_cluster_seed cluster_seed_type;
     float alpha;

vpr/src/pack/attraction_groups.cpp

@@ -1,4 +1,5 @@
 #include "attraction_groups.h"
+#include "globals.h"
 
 AttractionInfo::AttractionInfo(bool attraction_groups_on) {
     const auto& floorplanning_ctx = g_vpr_ctx.floorplanning();

vpr/src/pack/attraction_groups.h

@@ -10,8 +10,7 @@
 
 #include "vtr_strong_id.h"
 #include "vtr_vector.h"
-#include "atom_netlist.h"
-#include "globals.h"
+#include "atom_netlist_fwd.h"
 
 /**
  * @file
@@ -78,7 +77,7 @@ class AttractionInfo {
 
     void add_attraction_group(const AttractionGroup& group_info);
 
-    int num_attraction_groups();
+    int num_attraction_groups() const;
 
     int get_att_group_pulls() const;
 
@@ -118,7 +117,7 @@ inline void AttractionInfo::set_atom_attraction_group(const AtomBlockId atom_id,
     attraction_groups[group_id].group_atoms.push_back(atom_id);
 }
 
-inline int AttractionInfo::num_attraction_groups() {
+inline int AttractionInfo::num_attraction_groups() const {
     return attraction_groups.size();
 }
 

vpr/src/pack/cluster_util.cpp

@@ -1,6 +1,7 @@
 #ifndef CLUSTER_UTIL_H
 #define CLUSTER_UTIL_H
 
+#include <unordered_set>
 #include <vector>
 #include "cluster_legalizer.h"
 #include "pack_types.h"
@@ -63,18 +64,9 @@ struct t_molecule_stats {
     int num_used_ext_outputs = 0; //Number of *used external* output pins across all primitives in molecule
 };
 
-struct t_cluster_progress_stats {
-    int num_molecules = 0;
-    int num_molecules_processed = 0;
-    int mols_since_last_print = 0;
-    int blocks_since_last_analysis = 0;
-    int num_unrelated_clustering_attempts = 0;
-};
-
 /* Useful data structures for creating or modifying clusters */
 struct t_clustering_data {
-    int* hill_climbing_inputs_avail;
-
+    int unclustered_list_head_size = 0;
     /* Keeps a linked list of the unclustered blocks to speed up looking for *                                                                  
      * unclustered blocks with a certain number of *external* inputs.        *
      * [0..lut_size].  Unclustered_list_head[i] points to the head of the    *
@@ -83,16 +75,6 @@ struct t_clustering_data {
 
     //Maintaining a linked list of free molecule data for speed
     t_molecule_link* memory_pool = nullptr;
-
-    /* Does the atom block that drives the output of this atom net also appear as a   *
-     * receiver (input) pin of the atom net? If so, then by how much?
-     *
-     * This is used in the gain routines to avoid double counting the connections from   *
-     * the current cluster to other blocks (hence yielding better clusterings). *
-     * The only time an atom block should connect to the same atom net *
-     * twice is when one connection is an output and the other is an input, *
-     * so this should take care of all multiple connections.                */
-    std::unordered_map<AtomNetId, int> net_output_feeds_driving_block_input;
 };
 
 /***********************************/
@@ -112,8 +94,7 @@ void calc_init_packing_timing(const t_packer_opts& packer_opts,
 /*
  * @brief Free the clustering data structures.
  */
-void free_clustering_data(const t_packer_opts& packer_opts,
-                          t_clustering_data& clustering_data);
+void free_clustering_data(t_clustering_data& clustering_data);
 
 /*
  * @brief Check clustering legality and output it.
@@ -154,8 +135,6 @@ void remove_molecule_from_pb_stats_candidates(t_pack_molecule* molecule,
 void alloc_and_init_clustering(const t_molecule_stats& max_molecule_stats,
                                const Prepacker& prepacker,
                                t_clustering_data& clustering_data,
-                               std::unordered_map<AtomNetId, int>& net_output_feeds_driving_block_input,
-                               int& unclustered_list_head_size,
                                int num_molecules);
 
 /*
@@ -195,8 +174,7 @@ void print_pack_status_header();
 /*
  * @brief Incrementally print progress updates during clustering.
  */
-void print_pack_status(int num_clb,
-                       int tot_num_molecules,
+void print_pack_status(int tot_num_molecules,
                        int num_molecules_processed,
                        int& mols_since_last_print,
                        int device_width,
@@ -212,42 +190,6 @@ void print_pack_status(int num_clb,
 void rebuild_attraction_groups(AttractionInfo& attraction_groups,
                                const ClusterLegalizer& cluster_legalizer);
 
-/*
- * @brief Try to pack next_molecule into the given cluster. If this succeeds
- *        prepares the next_molecule with a new value to pack next iteration.
- *
- * This method will print the pack status and update the cluster stats.
- */
-void try_fill_cluster(ClusterLegalizer& cluster_legalizer,
-                      const Prepacker& prepacker,
-                      const t_packer_opts& packer_opts,
-                      t_pack_molecule*& prev_molecule,
-                      t_pack_molecule*& next_molecule,
-                      int& num_same_molecules,
-                      t_cluster_progress_stats& cluster_stats,
-                      int num_clb,
-                      const LegalizationClusterId legalization_cluster_id,
-                      AttractionInfo& attraction_groups,
-                      vtr::vector<LegalizationClusterId, std::vector<AtomNetId>>& clb_inter_blk_nets,
-                      bool allow_unrelated_clustering,
-                      const int& high_fanout_threshold,
-                      const std::unordered_set<AtomNetId>& is_clock,
-                      const std::unordered_set<AtomNetId>& is_global,
-                      const std::shared_ptr<SetupTimingInfo>& timing_info,
-                      e_block_pack_status& block_pack_status,
-                      t_molecule_link* unclustered_list_head,
-                      const int& unclustered_list_head_size,
-                      std::unordered_map<AtomNetId, int>& net_output_feeds_driving_block_input,
-                      std::map<const t_model*, std::vector<t_logical_block_type_ptr>>& primitive_candidate_block_types);
-
-void store_cluster_info_and_free(const t_packer_opts& packer_opts,
-                                 const LegalizationClusterId clb_index,
-                                 const t_logical_block_type_ptr logic_block_type,
-                                 const t_pb_type* le_pb_type,
-                                 std::vector<int>& le_count,
-                                 const ClusterLegalizer& cluster_legalizer,
-                                 vtr::vector<LegalizationClusterId, std::vector<AtomNetId>>& clb_inter_blk_nets);
-
 void update_connection_gain_values(const AtomNetId net_id,
                                    const AtomBlockId clustered_blk_id,
                                    t_pb* cur_pb,
@@ -260,7 +202,7 @@ void update_timing_gain_values(const AtomNetId net_id,
                                enum e_net_relation_to_clustered_block net_relation_to_clustered_block,
                                const SetupTimingInfo& timing_info,
                                const std::unordered_set<AtomNetId>& is_global,
-                               std::unordered_map<AtomNetId, int>& net_output_feeds_driving_block_input);
+                               const std::unordered_set<AtomNetId>& net_output_feeds_driving_block_input);
 
 /*
  * @brief Updates the marked data structures, and if gain_flag is GAIN, the gain
@@ -281,7 +223,7 @@ void mark_and_update_partial_gain(const AtomNetId net_id,
                                   const SetupTimingInfo& timing_info,
                                   const std::unordered_set<AtomNetId>& is_global,
                                   const int high_fanout_net_threshold,
-                                  std::unordered_map<AtomNetId, int>& net_output_feeds_driving_block_input);
+                                  const std::unordered_set<AtomNetId>& net_output_feeds_driving_block_input);
 
 /*
  * @brief Updates the total  gain array to reflect the desired tradeoff between
@@ -309,24 +251,7 @@ void update_cluster_stats(const t_pack_molecule* molecule,
                           const int high_fanout_net_threshold,
                           const SetupTimingInfo& timing_info,
                           AttractionInfo& attraction_groups,
-                          std::unordered_map<AtomNetId, int>& net_output_feeds_driving_block_input);
-
-/*
- * @brief Given a starting seed block, start_new_cluster determines the next
- *        cluster type to use.
- *
- * It expands the FPGA if it cannot find a legal cluster for the atom block
- */
-void start_new_cluster(ClusterLegalizer& cluster_legalizer,
-                       LegalizationClusterId& legalization_cluster_id,
-                       t_pack_molecule* molecule,
-                       std::map<t_logical_block_type_ptr, size_t>& num_used_type_instances,
-                       const float target_device_utilization,
-                       const t_arch* arch,
-                       const std::string& device_layout_name,
-                       const std::map<const t_model*, std::vector<t_logical_block_type_ptr>>& primitive_candidate_block_types,
-                       int verbosity,
-                       bool balance_block_type_utilization);
+                          const std::unordered_set<AtomNetId>& net_output_feeds_driving_block_input);
 
 /*
  * @brief Get candidate molecule to pack into currently open cluster
@@ -351,7 +276,7 @@ t_pack_molecule* get_highest_gain_molecule(t_pb* cur_pb,
                                            bool prioritize_transitive_connectivity,
                                            int transitive_fanout_threshold,
                                            const int feasible_block_array_size,
-                                           std::map<const t_model*, std::vector<t_logical_block_type_ptr>>& primitive_candidate_block_types);
+                                           const std::map<const t_model*, std::vector<t_logical_block_type_ptr>>& primitive_candidate_block_types);
 
 /*
  * @brief Add molecules with strong connectedness to the current cluster to the
@@ -392,7 +317,7 @@ void add_cluster_molecule_candidates_by_attraction_group(t_pb* cur_pb,
                                                          AttractionInfo& attraction_groups,
                                                          const int feasible_block_array_size,
                                                          LegalizationClusterId clb_index,
-                                                         std::map<const t_model*, std::vector<t_logical_block_type_ptr>>& primitive_candidate_block_types);
+                                                         const std::map<const t_model*, std::vector<t_logical_block_type_ptr>>& primitive_candidate_block_types);
 
 /*
  * @brief Add molecules based on transitive connections (eg. 2 hops away) with
@@ -421,7 +346,7 @@ t_pack_molecule* get_molecule_for_cluster(t_pb* cur_pb,
                                           int verbosity,
                                           t_molecule_link* unclustered_list_head,
                                           const int& unclustered_list_head_size,
-                                          std::map<const t_model*, std::vector<t_logical_block_type_ptr>>& primitive_candidate_block_types);
+                                          const std::map<const t_model*, std::vector<t_logical_block_type_ptr>>& primitive_candidate_block_types);
 
 /*
  * @brief Calculates molecule statistics for a single molecule.
@@ -455,6 +380,12 @@ void load_transitive_fanout_candidates(LegalizationClusterId cluster_index,
 
 std::map<const t_model*, std::vector<t_logical_block_type_ptr>> identify_primitive_candidate_block_types();
 
+/**
+ * @brief Identify which nets in the atom netlist are driven by the same atom
+ *        block that they appear as a receiver (input) pin of.
+ */
+std::unordered_set<AtomNetId> identify_net_output_feeds_driving_block_input(const AtomNetlist& atom_netlist);
+
 /**
  * @brief This function update the pb_type_count data structure by incrementing
  *        the number of used pb_types in the given packed cluster t_pb
@@ -465,7 +396,7 @@ size_t update_pb_type_count(const t_pb* pb, std::map<t_pb_type*, int>& pb_type_c
  * @brief This function updates the le_count data structure from the given
  *        packed cluster.
  */
-void update_le_count(const t_pb* pb, const t_logical_block_type_ptr logic_block_type, const t_pb_type* le_pb_type, std::vector<int>& le_count);
+void update_le_count(const t_pb* pb, const t_logical_block_type_ptr logic_block_type, const t_pb_type* le_pb_type, std::array<int, 3>& le_count);
 
 void print_pb_type_count_recurr(t_pb_type* type, size_t max_name_chars, size_t curr_depth, std::map<t_pb_type*, int>& pb_type_count);
 
@@ -478,7 +409,7 @@ void print_pb_type_count(const ClusteredNetlist& clb_nlist);
  * @brief This function identifies the logic block type which is defined by the
  *        block type which has a lut primitive.
  */
-t_logical_block_type_ptr identify_logic_block_type(std::map<const t_model*, std::vector<t_logical_block_type_ptr>>& primitive_candidate_block_types);
+t_logical_block_type_ptr identify_logic_block_type(const std::map<const t_model*, std::vector<t_logical_block_type_ptr>>& primitive_candidate_block_types);
 
 /*
  * @brief This function returns the pb_type that is similar to Logic Element (LE)
@@ -499,7 +430,7 @@ bool pb_used_for_blif_model(const t_pb* pb, const std::string& blif_model_name);
 /*
  * @brief Print the LE count data strurture.
  */
-void print_le_count(std::vector<int>& le_count, const t_pb_type* le_pb_type);
+void print_le_count(const std::array<int, 3>& le_count, const t_pb_type* le_pb_type);
 
 /*
  * @brief Given a pointer to a pb in a cluster, this routine returns a pointer