Merge pull request #1066 from arjenroodselaar/place_timeout

Timeout when legal placement can't be found for cell

3 files changed, 26 insertions, 6 deletions

diff --git a/common/kernel/command.cc b/common/kernel/command.cc
index c548509f..65aa0299 100644
--- a/common/kernel/command.cc
+++ b/common/kernel/command.cc
@@ -189,6 +189,8 @@ po::options_description CommandHandler::getGeneralOptions()
     general.add_options()("placer-heap-critexp", po::value<int>(),
                           "placer heap criticality exponent (int, default: 2)");
     general.add_options()("placer-heap-timingweight", po::value<int>(), "placer heap timing weight (int, default: 10)");
+    general.add_options()("placer-heap-cell-placement-timeout", po::value<int>(),
+            "allow placer to attempt up to max(10000, total cells^2 / N) iterations to place a cell (int N, default: 8, 0 for no timeout)");
 
 #if !defined(__wasm)
     general.add_options()("parallel-refine", "use new experimental parallelised engine for placement refinement");
@@ -328,6 +330,10 @@ void CommandHandler::setupContext(Context *ctx)
     if (vm.count("placer-heap-timingweight"))
         ctx->settings[ctx->id("placerHeap/timingWeight")] = std::to_string(vm["placer-heap-timingweight"].as<int>());
 
+    if (vm.count("placer-heap-cell-placement-timeout"))
+        ctx->settings[ctx->id("placerHeap/cellPlacementTimeout")] =
+            std::to_string(std::max(0, vm["placer-heap-cell-placement-timeout"].as<int>()));
+
     if (vm.count("parallel-refine"))
         ctx->settings[ctx->id("placerHeap/parallelRefine")] = true;
 
diff --git a/common/place/placer_heap.cc b/common/place/placer_heap.cc
index 339b88e7..7fa27206 100644
--- a/common/place/placer_heap.cc
+++ b/common/place/placer_heap.cc
@@ -218,7 +218,10 @@ class HeAPPlacer
 
         heap_runs.push_back(all_buckets);
         // The main HeAP placer loop
-        log_info("Running main analytical placer.\n");
+        if (cfg.cell_placement_timeout > 0)
+            log_info("Running main analytical placer, max placement attempts per cell = %d.\n", cfg.cell_placement_timeout);
+        else
+            log_info("Running main analytical placer.\n");
         while (stalled < 5 && (solved_hpwl <= legal_hpwl * 0.8)) {
             // Alternate between particular bel types and all bels
             for (auto &run : heap_runs) {
@@ -862,6 +865,7 @@ class HeAPPlacer
             int radius = 0;
             int iter = 0;
             int iter_at_radius = 0;
+            int total_iters_for_cell = 0;
             bool placed = false;
             BelId bestBel;
             int best_inp_len = std::numeric_limits<int>::max();
@@ -878,11 +882,9 @@ class HeAPPlacer
             }
 
             while (!placed) {
-
-                // Set a conservative timeout
-                if (iter > std::max(10000, 3 * int(ctx->cells.size())))
-                    log_error("Unable to find legal placement for cell '%s', check constraints and utilisation.\n",
-                              ctx->nameOf(ci));
+                if (cfg.cell_placement_timeout > 0 && total_iters_for_cell > cfg.cell_placement_timeout)
+                    log_error("Unable to find legal placement for cell '%s' after %d attempts, check constraints and utilisation. Use `--placer-heap-cell-placement-timeout` to change the number of attempts.\n",
+                              ctx->nameOf(ci), total_iters_for_cell);
 
                 // Determine a search radius around the solver location (which increases over time) that is clamped to
                 // the region constraint for the cell (if applicable)
@@ -1084,6 +1086,8 @@ class HeAPPlacer
                         break;
                     }
                 }
+
+                total_iters_for_cell++;
             }
         }
         auto endt = std::chrono::high_resolution_clock::now();
@@ -1814,6 +1818,15 @@ PlacerHeapCfg::PlacerHeapCfg(Context *ctx)
     solverTolerance = 1e-5;
     placeAllAtOnce = false;
 
+    int timeout_divisor = ctx->setting<int>("placerHeap/cellPlacementTimeout", 8);
+    if (timeout_divisor > 0) {
+        // Set a conservative default. This is a rather large number and could probably
+        // be shaved down, but for now it will keep the process from running indefinite.
+        cell_placement_timeout = std::max(10000, (int(ctx->cells.size()) * int(ctx->cells.size()) / timeout_divisor));
+    } else {
+        cell_placement_timeout = 0;
+    }
+
     hpwl_scale_x = 1;
     hpwl_scale_y = 1;
     spread_scale_x = 1;
diff --git a/common/place/placer_heap.h b/common/place/placer_heap.h
index 9c62869e..e554a8e0 100644
--- a/common/place/placer_heap.h
+++ b/common/place/placer_heap.h
@@ -42,6 +42,7 @@ struct PlacerHeapCfg
     float solverTolerance;
     bool placeAllAtOnce;
     bool parallelRefine;
+    int cell_placement_timeout;
 
     int hpwl_scale_x, hpwl_scale_y;
     int spread_scale_x, spread_scale_y;