placer1: Make budget-based placement an option

Signed-off-by: David Shah <davey1576@gmail.com>

common/command.cc

@@ -122,6 +122,8 @@ po::options_description CommandHandler::getGeneralOptions()
     general.add_options()("randomize-seed,r", "randomize seed value for random number generator");
     general.add_options()("slack_redist_iter", po::value<int>(), "number of iterations between slack redistribution");
     general.add_options()("cstrweight", po::value<float>(), "placer weighting for relative constraint satisfaction");
+    general.add_options()("placer-budgets", "use budget rather than criticality in placer timing weights");
+
     general.add_options()("pack-only", "pack design only without placement or routing");
 
     general.add_options()("ignore-loops", "ignore combinational loops in timing analysis");
@@ -187,6 +189,9 @@ void CommandHandler::setupContext(Context *ctx)
         settings->set("placer1/constraintWeight", vm["cstrweight"].as<float>());
     }
 
+    if (vm.count("placer-budgets")) {
+        settings->set("placer1/budgetBased", true);
+    }
     if (vm.count("freq")) {
         auto freq = vm["freq"].as<double>();
         if (freq > 0)

common/placer1.cc

@@ -45,8 +45,7 @@
 namespace std {
 template <> struct hash<std::pair<NEXTPNR_NAMESPACE_PREFIX IdString, std::size_t>>
 {
-        std::size_t
+    std::size_t operator()(const std::pair<NEXTPNR_NAMESPACE_PREFIX IdString, std::size_t> &idp) const noexcept
-        operator()(const std::pair<NEXTPNR_NAMESPACE_PREFIX IdString, std::size_t> &idp) const noexcept
     {
         std::size_t seed = 0;
         boost::hash_combine(seed, hash<NEXTPNR_NAMESPACE_PREFIX IdString>()(idp.first));
@@ -54,7 +53,7 @@ namespace std {
         return seed;
     }
 };
-}
+} // namespace std
 
 NEXTPNR_NAMESPACE_BEGIN
 
@@ -175,7 +174,7 @@ class SAPlacer
         if ((placed_cells - constr_placed_cells) % 500 != 0)
             log_info("  initial placement placed %d/%d cells\n", int(placed_cells - constr_placed_cells),
                      int(autoplaced.size()));
-        if (ctx->slack_redist_iter > 0)
+        if (cfg.budgetBased && ctx->slack_redist_iter > 0)
             assign_budget(ctx);
         ctx->yield();
         auto iplace_end = std::chrono::high_resolution_clock::now();
@@ -184,6 +183,7 @@ class SAPlacer
         log_info("Running simulated annealing placer.\n");
 
         // Invoke timing analysis to obtain criticalities
+        if (!cfg.budgetBased)
             get_criticalities(ctx, &net_crit);
 
         // Calculate costs after initial placement
@@ -280,15 +280,16 @@ class SAPlacer
                     ctx->shuffle(autoplaced);
 
                     // Legalisation is a big change so force a slack redistribution here
-                    if (ctx->slack_redist_iter > 0)
+                    if (ctx->slack_redist_iter > 0 && cfg.budgetBased)
                         assign_budget(ctx, true /* quiet */);
                 }
                 require_legal = false;
-            } else if (ctx->slack_redist_iter > 0 && iter % ctx->slack_redist_iter == 0) {
+            } else if (cfg.budgetBased && ctx->slack_redist_iter > 0 && iter % ctx->slack_redist_iter == 0) {
                 assign_budget(ctx, true /* quiet */);
             }
 
             // Invoke timing analysis to obtain criticalities
+            if (!cfg.budgetBased)
                 get_criticalities(ctx, &net_crit);
             // Need to rebuild costs after criticalities change
             setup_costs();
@@ -518,12 +519,17 @@ class SAPlacer
             return 0;
         if (ctx->getPortTimingClass(net->driver.cell, net->driver.port, cc) == TMG_IGNORE)
             return 0;
+        if (cfg.budgetBased) {
+            double delay = ctx->getDelayNS(ctx->predictDelay(net, net->users.at(user)));
+            return std::min(10.0, std::exp(delay - ctx->getDelayNS(net->users.at(user).budget)));
+        } else {
             auto crit = net_crit.find(net->name);
             if (crit == net_crit.end() || crit->second.criticality.empty())
                 return 0;
             double delay = ctx->getDelayNS(ctx->predictDelay(net, net->users.at(user)));
             return delay * std::pow(crit->second.criticality.at(user), crit_exp);
         }
+    }
 
     // Set up the cost maps
     void setup_costs()
@@ -690,6 +696,7 @@ Placer1Cfg::Placer1Cfg(Context *ctx) : Settings(ctx)
 {
     constraintWeight = get<float>("placer1/constraintWeight", 10);
     minBelsForGridPick = get<int>("placer1/minBelsForGridPick", 64);
+    budgetBased = get<bool>("placer1/budgetBased", false);
 }
 
 bool placer1(Context *ctx, Placer1Cfg cfg)

common/placer1.h

@@ -29,6 +29,7 @@ struct Placer1Cfg : public Settings
     Placer1Cfg(Context *ctx);
     float constraintWeight;
     int minBelsForGridPick;
+    bool budgetBased;
 };
 
 extern bool placer1(Context *ctx, Placer1Cfg cfg);