alloc_lookups_and_delay_model returns a unique_ptr instead of shared_ptr

Author: soheilshahrouz

vpr/src/place/place_delay_model.cpp

@@ -318,7 +318,7 @@ void OverrideDelayModel::write(const std::string& file) const {
 #endif
 
 ///@brief Initialize the placer delay model.
-std::shared_ptr<PlaceDelayModel> alloc_lookups_and_delay_model(const Netlist<>& net_list,
+std::unique_ptr<PlaceDelayModel> alloc_lookups_and_delay_model(const Netlist<>& net_list,
                                                                t_chan_width_dist chan_width_dist,
                                                                const t_placer_opts& placer_opts,
                                                                const t_router_opts& router_opts,

vpr/src/place/place_delay_model.h

@@ -29,7 +29,7 @@ class PlaceDelayModel;
 class PlacerState;
 
 ///@brief Initialize the placer delay model.
-std::shared_ptr<PlaceDelayModel> alloc_lookups_and_delay_model(const Netlist<>& net_list,
+std::unique_ptr<PlaceDelayModel> alloc_lookups_and_delay_model(const Netlist<>& net_list,
                                                                t_chan_width_dist chan_width_dist,
                                                                const t_placer_opts& place_opts,
                                                                const t_router_opts& router_opts,

vpr/src/place/placer.cpp

@@ -281,7 +281,7 @@ void Placer::place() {
 
    bool skip_anneal = false;
 #ifdef ENABLE_ANALYTIC_PLACE
-   // When enabled, skip most of the annealing and go straight to quench
+   // Cluster-level analytic placer: when enabled, skip most of the annealing and go straight to quench
    if (placer_opts_.enable_analytic_placer) {
        skip_anneal = true;
    }

vpr/src/place/placer.h

@@ -79,7 +79,11 @@ class Placer {
 
     /// Stores a placement state as a retrievable checkpoint in case the placement quality deteriorates later.
     t_placement_checkpoint placement_checkpoint_;
-    /// It holds a setup timing analysis engine. Other placement timing object usually have a reference or pointer to timing_info.
+    /**
+     * @brief Holds a setup timing analysis engine.
+     * Other placement timing objects like PlacerSetupSlacks, PlacerCriticalities, and NetPinTimingInvalidator
+     * have a pointer to timing_info. A shared pointer is used to manage the lifetime of the object.
+     */
     std::shared_ptr<SetupTimingInfo> timing_info_;
     /// Post-clustering delay calculator. Its API allows extraction of delay for each timing edge.
     std::shared_ptr<PlacementDelayCalculator> placement_delay_calc_;

vpr/src/place/timing_place_lookup.cpp

@@ -170,7 +170,7 @@ static float find_neighboring_average(vtr::NdMatrix<float, 4>& matrix,
 
 /******* Globally Accessible Functions **********/
 
-std::shared_ptr<PlaceDelayModel> compute_place_delay_model(const t_placer_opts& placer_opts,
+std::unique_ptr<PlaceDelayModel> compute_place_delay_model(const t_placer_opts& placer_opts,
                                                            const t_router_opts& router_opts,
                                                            const Netlist<>& net_list,
                                                            t_det_routing_arch* det_routing_arch,
@@ -196,15 +196,15 @@ std::shared_ptr<PlaceDelayModel> compute_place_delay_model(const t_placer_opts&
     int longest_length = get_longest_segment_length(segment_inf);
 
     /*now setup and compute the actual arrays */
-    std::shared_ptr<PlaceDelayModel> place_delay_model;
+    std::unique_ptr<PlaceDelayModel> place_delay_model;
     float min_cross_layer_delay = get_min_cross_layer_delay();
 
     if (placer_opts.delay_model_type == PlaceDelayModelType::SIMPLE) {
-        place_delay_model = std::make_shared<SimpleDelayModel>();
+        place_delay_model = std::make_unique<SimpleDelayModel>();
     } else if (placer_opts.delay_model_type == PlaceDelayModelType::DELTA) {
-        place_delay_model = std::make_shared<DeltaDelayModel>(min_cross_layer_delay, is_flat);
+        place_delay_model = std::make_unique<DeltaDelayModel>(min_cross_layer_delay, is_flat);
     } else if (placer_opts.delay_model_type == PlaceDelayModelType::DELTA_OVERRIDE) {
-        place_delay_model = std::make_shared<OverrideDelayModel>(min_cross_layer_delay, is_flat);
+        place_delay_model = std::make_unique<OverrideDelayModel>(min_cross_layer_delay, is_flat);
     } else {
         VTR_ASSERT_MSG(false, "Invalid placer delay model");
     }

vpr/src/place/timing_place_lookup.h

@@ -2,7 +2,7 @@
 #define TIMING_PLACE_LOOKUP_H
 #include "place_delay_model.h"
 
-std::shared_ptr<PlaceDelayModel> compute_place_delay_model(const t_placer_opts& placer_opts,
+std::unique_ptr<PlaceDelayModel> compute_place_delay_model(const t_placer_opts& placer_opts,
                                                            const t_router_opts& router_opts,
                                                            const Netlist<>& net_list,
                                                            t_det_routing_arch* det_routing_arch,