recompute congestion cost when estimating channel utilization

Author: soheilshahrouz

vpr/src/place/annealer.cpp

@@ -671,6 +671,12 @@ void PlacementAnnealer::outer_loop_update_timing_info() {
         outer_crit_iter_count_++;
     }
 
+    if (congestion_modeling_started_
+        || (placer_stats_.success_rate < placer_opts_.congestion_acceptance_rate_trigger && placer_stats_.av_cost != 0.)) {
+        costs_.congestion_cost = net_cost_handler_.estimate_routing_chann_util();
+        congestion_modeling_started_ = true;
+    }
+
     // Update the cost normalization factors
     costs_.update_norm_factors();
 

vpr/src/place/net_cost_handler.cpp

@@ -300,7 +300,7 @@ std::tuple<double, double, double> NetCostHandler::comp_cube_bb_cong_cost_(e_cos
     }
 
     // Now that all bounding boxes are computed from scratch, we recompute the channel utilization
-    estimate_routing_chann_util();
+//    estimate_routing_chann_util();
 
     // Compute congestion cost using recomputed bounding boxes and channel utilization map
     for (ClusterNetId net_id : cluster_ctx.clb_nlist.nets()) {
@@ -1564,8 +1564,8 @@ std::pair<double, double> NetCostHandler::recompute_bb_cong_cost_() {
 }
 
 static double wirelength_crossing_count(size_t fanout) {
-    /* Get the expected "crossing count" of a net, based on its number *
-     * of pins.  Extrapolate for very large nets.                      */
+    /* Get the expected "crossing count" of a net, based on its number
+     * of pins.  Extrapolate for very large nets. */
 
     if (fanout > MAX_FANOUT_CROSSING_COUNT) {
         return 2.7933 + 0.02616 * (fanout - MAX_FANOUT_CROSSING_COUNT);
@@ -1710,7 +1710,7 @@ double NetCostHandler::get_total_wirelength_estimate() const {
     return estimated_wirelength;
 }
 
-void NetCostHandler::estimate_routing_chann_util() {
+double NetCostHandler::estimate_routing_chann_util() {
     const auto& cluster_ctx = g_vpr_ctx.clustering();
     const auto& device_ctx = g_vpr_ctx.device();
 
@@ -1757,6 +1757,17 @@ void NetCostHandler::estimate_routing_chann_util() {
 
     acc_chanx_util_ = vtr::PrefixSum2D<double>(chanx_util_);
     acc_chany_util_ = vtr::PrefixSum2D<double>(chany_util_);
+
+    double cong_cost = 0.;
+    // Compute congestion cost using recomputed bounding boxes and channel utilization map
+    for (ClusterNetId net_id : cluster_ctx.clb_nlist.nets()) {
+        if (!cluster_ctx.clb_nlist.net_is_ignored(net_id)) {
+            net_cong_cost_[net_id] = get_net_cube_cong_cost_(net_id, /*use_ts=*/false);
+            cong_cost += net_cong_cost_[net_id];
+        }
+    }
+
+    return cong_cost;
 }
 
 void NetCostHandler::set_ts_bb_coord_(const ClusterNetId net_id) {

vpr/src/place/net_cost_handler.h

@@ -127,7 +127,7 @@ class NetCostHandler {
      */
     double get_total_wirelength_estimate() const;
 
-    void estimate_routing_chann_util();
+    double estimate_routing_chann_util();
 
   private:
     ///@brief Specifies whether the bounding box is computed using cube method or per-layer method.