Merge pull request #3162 from AlexandreSinger/feature-packer-state

AlexandreSinger · web-flow · commit ae57c3f643e9 · 2025-06-26T14:25:41.000-04:00
[Packer] Reorganized Iterative Packer Algorithm
diff --git a/vpr/src/pack/pack.cpp b/vpr/src/pack/pack.cpp
@@ -22,11 +22,122 @@
 #include "vtr_assert.h"
 #include "vtr_log.h"
 
+namespace {
+
+/**
+ * @brief Enumeration for the state of the packer.
+ *
+ * If the packer fails to find a dense enough packing, depending on how the
+ * packer failed, the packer may iteratively retry packing with different
+ * settings to try and find a denser packing. These states represent a
+ * different type of iteration.
+ */
+enum class e_packer_state {
+    /// @brief Default packer state.
+    DEFAULT,
+    /// @brief Succcess state for the packer. The packing looks feasible to
+    ///        fit on the device (does not exceed number of blocks of each
+    ///        type in the grid) and meets floorplanning constraints.
+    SUCCESS,
+    /// @brief Standard fallback where there are no region constraints. Turns
+    ///        on unrelated clustering and balanced packing if it can.
+    UNRELATED_AND_BALANCED,
+    /// @brief Region constraints: Turns on attraction groups for overfilled regions.
+    ATTRACTION_GROUPS,
+    /// @brief Region constraints: Turns on more attraction groups for overfilled regions.
+    MORE_ATTRACTION_GROUPS,
+    /// @brief Region constraints: Turns on more attraction groups for all regions.
+    ATTRACTION_GROUPS_ALL_REGIONS,
+    /// @brief Region constraints: Turns on more attraction groups for all regions
+    ///        and increases the target density of "clb" blocks.
+    ///        TODO: This should increase the target density of all overused blocks.
+    ATTRACTION_GROUPS_ALL_REGIONS_AND_INCREASED_TARGET_DENSITY,
+    /// @brief The failure state.
+    FAILURE
+};
+
+} // namespace
+
 static bool try_size_device_grid(const t_arch& arch,
                                  const std::map<t_logical_block_type_ptr, size_t>& num_type_instances,
                                  float target_device_utilization,
                                  const std::string& device_layout_name);
 
+/**
+ * @brief The packer iteratively re-packes the netlist if it fails to find a
+ *        valid clustering. Each iteration is a state the packer is in, where
+ *        each state uses a different set of options. This method gets the next
+ *        state of the packer given the current state of the packer.
+ *
+ *  @param current_packer_state
+ *      The current state of the packer (the state used to make the most recent
+ *      clustering).
+ *  @param fits_on_device
+ *      Whether the current clustering fits on the device or not.
+ *  @param floorplan_regions_overfull
+ *      Whether the current clustering has overfilled regions.
+ *  @param floorplan_not_fitting
+ *      Whether the current clustering is fitting on the current floorplan.
+ */
+static e_packer_state get_next_packer_state(e_packer_state current_packer_state,
+                                            bool fits_on_device,
+                                            bool floorplan_regions_overfull,
+                                            bool floorplan_not_fitting) {
+    // Next packer state logic
+    e_packer_state next_packer_state = e_packer_state::FAILURE;
+    if (fits_on_device && !floorplan_regions_overfull) {
+        // If everything fits on the device and the floorplan regions are
+        // not overfilled, the next state is success.
+        next_packer_state = e_packer_state::SUCCESS;
+    } else {
+        if (floorplan_not_fitting) {
+            // If there are overfilled region constraints.
+
+            // When running with tight floorplan constraints, some regions may become overfull with clusters (i.e.
+            // the number of blocks assigned to the region exceeds the number of blocks available). When this occurs, we
+            // cluster more densely to be able to adhere to the floorplan constraints. However, we do not want to cluster more
+            // densely unnecessarily, as this can negatively impact wirelength. So, we have iterative approach. We check at the end
+            // of every iteration if any floorplan regions are overfull. In the first iteration, we run
+            // with no attraction groups (not packing more densely). If regions are overfull at the end of the first iteration,
+            // we create attraction groups for partitions with overfull regions (pack those atoms more densely). We continue this way
+            // until the last iteration, when we create attraction groups for every partition, if needed.
+
+            switch (current_packer_state) {
+                case e_packer_state::DEFAULT:
+                    next_packer_state = e_packer_state::ATTRACTION_GROUPS;
+                    break;
+                case e_packer_state::UNRELATED_AND_BALANCED:
+                case e_packer_state::ATTRACTION_GROUPS:
+                    next_packer_state = e_packer_state::MORE_ATTRACTION_GROUPS;
+                    break;
+                case e_packer_state::MORE_ATTRACTION_GROUPS:
+                    next_packer_state = e_packer_state::ATTRACTION_GROUPS_ALL_REGIONS;
+                    break;
+                case e_packer_state::ATTRACTION_GROUPS_ALL_REGIONS:
+                    next_packer_state = e_packer_state::ATTRACTION_GROUPS_ALL_REGIONS_AND_INCREASED_TARGET_DENSITY;
+                    break;
+                case e_packer_state::ATTRACTION_GROUPS_ALL_REGIONS_AND_INCREASED_TARGET_DENSITY:
+                default:
+                    next_packer_state = e_packer_state::FAILURE;
+                    break;
+            }
+        } else {
+            // If there are no overfilled region constraints, but some block
+            // types on the grid are overfilled.
+            switch (current_packer_state) {
+                case e_packer_state::DEFAULT:
+                    next_packer_state = e_packer_state::UNRELATED_AND_BALANCED;
+                    break;
+                default:
+                    next_packer_state = e_packer_state::FAILURE;
+                    break;
+            }
+        }
+    }
+
+    return next_packer_state;
+}
+
 bool try_pack(const t_packer_opts& packer_opts,
               const t_analysis_opts& analysis_opts,
               const t_ap_opts& ap_opts,
@@ -145,7 +256,10 @@ bool try_pack(const t_packer_opts& packer_opts,
 
     g_vpr_ctx.mutable_atom().mutable_lookup().set_atom_pb_bimap_lock(true);
 
-    while (true) {
+    // The current state of the packer during iterative packing.
+    e_packer_state current_packer_state = e_packer_state::DEFAULT;
+
+    while (current_packer_state != e_packer_state::SUCCESS && current_packer_state != e_packer_state::FAILURE) {
         //Cluster the netlist
         //  num_used_type_instances: A map used to save the number of used
         //                           instances from each logical block type.
@@ -157,7 +271,7 @@ bool try_pack(const t_packer_opts& packer_opts,
                                                           attraction_groups,
                                                           mutable_device_ctx);
 
-        //Try to size/find a device
+        // Try to size/find a device
         bool fits_on_device = try_size_device_grid(arch, num_used_type_instances, packer_opts.target_device_utilization, packer_opts.device_layout);
 
         /* We use this bool to determine the cause for the clustering not being dense enough. If the clustering
@@ -170,48 +284,56 @@ bool try_pack(const t_packer_opts& packer_opts,
 
         bool floorplan_not_fitting = (floorplan_regions_overfull || g_vpr_ctx.floorplanning().constraints.get_num_partitions() > 0);
 
-        if (fits_on_device && !floorplan_regions_overfull) {
-            break; //Done
-        } else if (pack_iteration == 1 && !floorplan_not_fitting) {
-            //1st pack attempt was unsuccessful (i.e. not dense enough) and we have control of unrelated clustering
-            //
-            //Turn it on to increase packing density
-            if (packer_opts.allow_unrelated_clustering == e_unrelated_clustering::AUTO) {
-                VTR_ASSERT(allow_unrelated_clustering == false);
-                allow_unrelated_clustering = true;
+        // Next packer state logic
+        e_packer_state next_packer_state = get_next_packer_state(current_packer_state,
+                                                                 fits_on_device,
+                                                                 floorplan_regions_overfull,
+                                                                 floorplan_not_fitting);
+
+        // Set up for the options used for the next packer state.
+        // NOTE: This must be done here (and not at the start of the next packer
+        //       iteration) since we need to know information about the current
+        //       clustering to change the options for the next iteration.
+        switch (next_packer_state) {
+            case e_packer_state::UNRELATED_AND_BALANCED: {
+                // 1st pack attempt was unsuccessful (i.e. not dense enough) and we have control of unrelated clustering
+                //
+                // Turn it on to increase packing density
+                // TODO: This will have no affect if unrelated clustering and
+                //       balance block type utilization is not auto. Should update
+                //       the next state logic.
+                if (packer_opts.allow_unrelated_clustering == e_unrelated_clustering::AUTO) {
+                    VTR_ASSERT(allow_unrelated_clustering == false);
+                    allow_unrelated_clustering = true;
+                }
+                if (packer_opts.balance_block_type_utilization == e_balance_block_type_util::AUTO) {
+                    VTR_ASSERT(balance_block_type_util == false);
+                    balance_block_type_util = true;
+                }
+                VTR_LOG("Packing failed to fit on device. Re-packing with: unrelated_logic_clustering=%s balance_block_type_util=%s\n",
+                        (allow_unrelated_clustering ? "true" : "false"),
+                        (balance_block_type_util ? "true" : "false"));
+                break;
             }
-            if (packer_opts.balance_block_type_utilization == e_balance_block_type_util::AUTO) {
-                VTR_ASSERT(balance_block_type_util == false);
-                balance_block_type_util = true;
+            case e_packer_state::ATTRACTION_GROUPS: {
+                VTR_LOG("Floorplan regions are overfull: trying to pack again using cluster attraction groups. \n");
+                attraction_groups.create_att_groups_for_overfull_regions(overfull_partition_regions);
+                attraction_groups.set_att_group_pulls(1);
+                break;
             }
-            VTR_LOG("Packing failed to fit on device. Re-packing with: unrelated_logic_clustering=%s balance_block_type_util=%s\n",
-                    (allow_unrelated_clustering ? "true" : "false"),
-                    (balance_block_type_util ? "true" : "false"));
-            /*
-             * When running with tight floorplan constraints, some regions may become overfull with clusters (i.e.
-             * the number of blocks assigned to the region exceeds the number of blocks available). When this occurs, we
-             * cluster more densely to be able to adhere to the floorplan constraints. However, we do not want to cluster more
-             * densely unnecessarily, as this can negatively impact wirelength. So, we have iterative approach. We check at the end
-             * of every iteration if any floorplan regions are overfull. In the first iteration, we run
-             * with no attraction groups (not packing more densely). If regions are overfull at the end of the first iteration,
-             * we create attraction groups for partitions with overfull regions (pack those atoms more densely). We continue this way
-             * until the last iteration, when we create attraction groups for every partition, if needed.
-             */
-        } else if (pack_iteration == 1 && floorplan_not_fitting) {
-            VTR_LOG("Floorplan regions are overfull: trying to pack again using cluster attraction groups. \n");
-            attraction_groups.create_att_groups_for_overfull_regions(overfull_partition_regions);
-            attraction_groups.set_att_group_pulls(1);
-
-        } else if (pack_iteration >= 2 && pack_iteration < 5 && floorplan_not_fitting) {
-            if (pack_iteration == 2) {
+            case e_packer_state::MORE_ATTRACTION_GROUPS: {
                 VTR_LOG("Floorplan regions are overfull: trying to pack again with more attraction groups exploration. \n");
                 attraction_groups.create_att_groups_for_overfull_regions(overfull_partition_regions);
                 VTR_LOG("Pack iteration is %d\n", pack_iteration);
-            } else if (pack_iteration == 3) {
+                break;
+            }
+            case e_packer_state::ATTRACTION_GROUPS_ALL_REGIONS: {
                 attraction_groups.create_att_groups_for_all_regions();
                 VTR_LOG("Floorplan regions are overfull: trying to pack again with more attraction groups exploration. \n");
                 VTR_LOG("Pack iteration is %d\n", pack_iteration);
-            } else if (pack_iteration == 4) {
+                break;
+            }
+            case e_packer_state::ATTRACTION_GROUPS_ALL_REGIONS_AND_INCREASED_TARGET_DENSITY: {
                 attraction_groups.create_att_groups_for_all_regions();
                 VTR_LOG("Floorplan regions are overfull: trying to pack again with more attraction groups exploration and higher target pin utilization. \n");
                 VTR_LOG("Pack iteration is %d\n", pack_iteration);
@@ -224,9 +346,18 @@ bool try_pack(const t_packer_opts& packer_opts,
                 //       do it for all block types. Doing it only for a clb
                 //       string is dangerous -VB.
                 cluster_legalizer.get_target_external_pin_util().set_block_pin_util("clb", pin_util);
+                break;
             }
+            case e_packer_state::DEFAULT:
+            case e_packer_state::SUCCESS:
+            case e_packer_state::FAILURE:
+            default:
+                // Nothing to set up.
+                break;
+        }
 
-        } else { //Unable to pack densely enough: Give Up
+        // Raise an error if the packer failed to pack.
+        if (next_packer_state == e_packer_state::FAILURE) {
             if (floorplan_regions_overfull) {
                 VPR_FATAL_ERROR(VPR_ERROR_OTHER,
                                 "Failed to find pack clusters densely enough to fit in the designated floorplan regions.\n"
@@ -255,14 +386,23 @@ bool try_pack(const t_packer_opts& packer_opts,
             VPR_FATAL_ERROR(VPR_ERROR_OTHER, "Failed to find device which satisfies resource requirements required: %s (available %s)", resource_reqs.c_str(), resource_avail.c_str());
         }
 
-        //Reset floorplanning constraints for re-packing
-        g_vpr_ctx.mutable_floorplanning().cluster_constraints.clear();
+        // If the packer was unsuccessful, reset the packed solution and try again.
+        if (next_packer_state != e_packer_state::SUCCESS) {
+            // Reset floorplanning constraints for re-packing
+            g_vpr_ctx.mutable_floorplanning().cluster_constraints.clear();
+
+            // Reset the cluster legalizer for re-clustering.
+            cluster_legalizer.reset();
+        }
+
+        // Set the current state to the next state.
+        current_packer_state = next_packer_state;
 
-        // Reset the cluster legalizer for re-clustering.
-        cluster_legalizer.reset();
         ++pack_iteration;
     }
 
+    VTR_ASSERT(current_packer_state == e_packer_state::SUCCESS);
+
     /* Packing iterative improvement can be done here */
     /*       Use the re-cluster API to edit it        */
     /******************* Start *************************/
