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AlexandreSingerAlexandreSinger
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[AP][DetailedPlacer] Added Detailed Placer Class
The Detailed Placer is a pass in the AP flow which takes a legal placement and optimizes it, while still remaining legal. Previously in the AP flow, the annealer from the Placement stage was always used to optimize the placement. Now the user can choose to not use the annealer, by selecting the "none" Detailed Placer. Other Detailed Placers can now also be added to explore other Detailed Placement algorithms in VTR.
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‎doc/src/vpr/command_line_usage.rst

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@@ -1198,6 +1198,16 @@ Analytical Placement is generally split into three stages:
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**Default:** ``appack``
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.. option:: --ap_detailed_placer {none | annealer}
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Controls which Detailed Placer to use in the AP Flow.
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* ``none`` Do not use any Detailed Placer.
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* ``annealer`` Use the Annealer from the Placement stage as a Detailed Placer. This will use the same Placer Options from the Place stage to configure the annealer.
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**Default:** ``annealer``
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.. _router_options:
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‎vpr/src/analytical_place/analytical_placement_flow.cpp

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#include "analytical_solver.h"
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#include "ap_netlist.h"
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#include "atom_netlist.h"
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#include "detailed_placer.h"
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#include "full_legalizer.h"
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#include "gen_ap_netlist_from_atoms.h"
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#include "global_placer.h"
@@ -106,5 +107,19 @@ void run_analytical_placement_flow(t_vpr_setup& vpr_setup) {
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*device_ctx.arch,
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device_ctx.grid);
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full_legalizer->legalize(p_placement);
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// Run the Detailed Placer.
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std::unique_ptr<DetailedPlacer> detailed_placer = make_detailed_placer(ap_opts.detailed_placer_type,
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g_vpr_ctx.placement().blk_loc_registry(),
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atom_nlist,
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g_vpr_ctx.clustering().clb_nlist,
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vpr_setup,
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*device_ctx.arch);
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detailed_placer->optimize_placement();
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// Clean up some of the global variables that will no longer be used outside
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// of this flow.
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g_vpr_ctx.mutable_placement().clean_placement_context_post_place();
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g_vpr_ctx.mutable_floorplanning().clean_floorplanning_context_post_place();
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}
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‎vpr/src/analytical_place/ap_flow_enums.h

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@@ -18,3 +18,14 @@ enum class e_ap_full_legalizer {
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APPack ///< The APPack Full Legalizer, which uses the flat placement to improve the Packer and Placer.
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};
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/**
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* @brief The type of a Detailed Placer.
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*
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* The Analytical Placement flow may implement different Detailed Placers. This
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* enum can select between these different Detailed Placers.
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*/
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enum class e_ap_detailed_placer {
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Identity, ///< The Identity Detailed Placer, which does not perform any optimizations on the legalized placement. Needed as a placeholder.
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Annealer ///< The Annealer Detailed Placer, which runs the annealer found in the Place part of the VPR flow (using the same options as the Placement stage).
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};
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‎vpr/src/analytical_place/detailed_placer.cpp

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/**
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* @file
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* @author Alex Singer
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* @date February 2025
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* @brief Implementation of the Detailed Placers.
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*/
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#include "detailed_placer.h"
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#include <memory>
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#include "FlatPlacementInfo.h"
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#include "PlacementDelayModelCreator.h"
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#include "ap_flow_enums.h"
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#include "atom_netlist.h"
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#include "clustered_netlist.h"
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#include "clustered_netlist_utils.h"
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#include "echo_files.h"
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#include "globals.h"
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#include "physical_types.h"
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#include "place_and_route.h"
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#include "place_delay_model.h"
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#include "placer.h"
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#include "vpr_error.h"
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#include "vpr_types.h"
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#include "vpr_utils.h"
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std::unique_ptr<DetailedPlacer> make_detailed_placer(
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e_ap_detailed_placer detailed_placer_type,
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const BlkLocRegistry& curr_clustered_placement,
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const AtomNetlist& atom_netlist,
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const ClusteredNetlist& clustered_netlist,
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t_vpr_setup& vpr_setup,
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const t_arch& arch) {
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switch (detailed_placer_type) {
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case e_ap_detailed_placer::Identity:
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return std::make_unique<IdentityDetailedPlacer>();
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case e_ap_detailed_placer::Annealer:
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return std::make_unique<AnnealerDetailedPlacer>(
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curr_clustered_placement,
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atom_netlist,
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clustered_netlist,
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vpr_setup,
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arch);
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default:
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VPR_FATAL_ERROR(VPR_ERROR_AP,
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"Unrecognized detailed placer type");
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}
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}
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AnnealerDetailedPlacer::AnnealerDetailedPlacer(
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const BlkLocRegistry& curr_clustered_placement,
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const AtomNetlist& atom_netlist,
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const ClusteredNetlist& clustered_netlist,
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t_vpr_setup& vpr_setup,
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const t_arch& arch)
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: DetailedPlacer(),
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// TODO: These two variables needed to be stored in the class since
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// the Placer stores a reference to these objects. These
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// should really be initialized and stored into the Placer
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// class directly.
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pb_gpin_lookup_(g_vpr_ctx.device().logical_block_types),
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netlist_pin_lookup_(clustered_netlist, atom_netlist, pb_gpin_lookup_) {
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// Initialize the place delay model.
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// TODO: This initialization is complicated. Should be moved within create_delay_model
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// or something.
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std::shared_ptr<PlaceDelayModel> place_delay_model;
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if (vpr_setup.PlacerOpts.place_algorithm.is_timing_driven()) {
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place_delay_model = PlacementDelayModelCreator::create_delay_model(vpr_setup.PlacerOpts,
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vpr_setup.RouterOpts,
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(const Netlist<>&)clustered_netlist,
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&vpr_setup.RoutingArch,
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vpr_setup.Segments,
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arch.Chans,
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arch.directs,
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false /*is_flat*/);
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if (isEchoFileEnabled(E_ECHO_PLACEMENT_DELTA_DELAY_MODEL)) {
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place_delay_model->dump_echo(getEchoFileName(E_ECHO_PLACEMENT_DELTA_DELAY_MODEL));
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}
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}
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placer_ = std::make_unique<Placer>((const Netlist<>&)clustered_netlist,
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curr_clustered_placement,
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vpr_setup.PlacerOpts,
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vpr_setup.AnalysisOpts,
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vpr_setup.NocOpts,
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pb_gpin_lookup_,
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netlist_pin_lookup_,
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FlatPlacementInfo(),
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place_delay_model,
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g_vpr_ctx.placement().cube_bb,
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false /*is_flat*/,
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false /*quiet*/);
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}
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void AnnealerDetailedPlacer::optimize_placement() {
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// Prevent the annealer from directly modifying the global legal placement.
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// It should only modify its own, local placement.
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g_vpr_ctx.mutable_placement().lock_loc_vars();
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// Run the simulated annealer.
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placer_->place();
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// Copy the placement solution into the global placement solution.
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placer_->copy_locs_to_global_state(g_vpr_ctx.mutable_placement());
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// Since the placement was modified, need to resyncronize the pins in the
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// clusters.
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post_place_sync();
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}
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‎vpr/src/analytical_place/detailed_placer.h

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/**
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* @file
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* @author Alex Singer
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* @date February 2025
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* @brief Defines the DetailedPlacer class which takes a fully legal clustering
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* and placement and optimizes them while remaining legal.
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*/
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#pragma once
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#include <memory>
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#include "ap_flow_enums.h"
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#include "clustered_netlist_utils.h"
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#include "placer.h"
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#include "vpr_utils.h"
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/**
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* @brief The detailed placer in an AP flow.
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*
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* Given a fully legal clustering and clustered placement, will optimize the
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* solution while remaining fully legal (able to be used in the rest of the VPR
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* flow).
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*/
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class DetailedPlacer {
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public:
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virtual ~DetailedPlacer() {}
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DetailedPlacer() = default;
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/**
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* @brief Optimize the current legal placement.
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*/
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virtual void optimize_placement() = 0;
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};
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/**
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* @brief A factory method which creates a Detailed Placer of the given type.
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*/
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std::unique_ptr<DetailedPlacer> make_detailed_placer(
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e_ap_detailed_placer detailed_placer_type,
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const BlkLocRegistry& curr_clustered_placement,
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const AtomNetlist& atom_netlist,
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const ClusteredNetlist& clustered_netlist,
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t_vpr_setup& vpr_setup,
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const t_arch& arch);
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/**
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* @brief The Identity Detailed Placer.
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*
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* This detailed placer does literally nothing to the legal placement. This
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* class is used as a placeholder to make the higher-level code easier to work
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* with.
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*/
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class IdentityDetailedPlacer : public DetailedPlacer {
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public:
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using DetailedPlacer::DetailedPlacer;
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void optimize_placement() final {}
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};
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/**
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* @brief The Annealer Detailed Placer.
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*
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* This Detailed Placer passes the legal solution into the Annealer in the
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* VPR flow (uses the legal solution as the initial placement). This performs
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* the Simulated Annealing algorithm on the solution at the cluster level to
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* try and find a better clustered placement.
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*
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* This Detailed Placer reuses the options from the Placer stage of VPR for this
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* stage. So options passed to the Placer will be used in here.
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*/
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class AnnealerDetailedPlacer : public DetailedPlacer {
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public:
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/**
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* @brief Construct the Annealer Detailed Placer class.
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*
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* @param curr_clustered_placement
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* The legalized placement solution to pass as the initial placement
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* into the annealer.
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* @param atom_netlist
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* The netlist of atoms in the circuit.
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* @param clustered_netlist
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* The netlist of clusters created by the Full Legalizer.
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* @param vpr_setup
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* The setup variables, used to get the params from the user.
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* @param arch
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* The FPGA architecture to optimize onto.
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*/
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AnnealerDetailedPlacer(const BlkLocRegistry& curr_clustered_placement,
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const AtomNetlist& atom_netlist,
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const ClusteredNetlist& clustered_netlist,
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t_vpr_setup& vpr_setup,
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const t_arch& arch);
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/**
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* @brief Run the annealer.
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*/
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void optimize_placement() final;
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private:
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/// @brief The placer class, which contains the annealer.
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std::unique_ptr<Placer> placer_;
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/// @brief A lookup between the block pin indices and pb graph pins.
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IntraLbPbPinLookup pb_gpin_lookup_;
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/// @brief A lookup between CLB pins and atom pins.
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ClusteredPinAtomPinsLookup netlist_pin_lookup_;
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};
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