grt: disable multiple NDR nets at once if there is too much congestion

Signed-off-by: Jonas Gava <[email protected]>

Author: jfgava

src/grt/src/fastroute/include/FastRoute.h

@@ -253,6 +253,7 @@ class FastRouteCore
   void computeCongestedNDRnets();
   void updateSoftNDRNetUsage(int net_id, int edge_cost);
   void setSoftNDR(int net_id);
+  void applySoftNDR(const std::vector<int>& net_ids);
 
   int x_corner() const { return x_corner_; }
   int y_corner() const { return y_corner_; }

src/grt/src/fastroute/include/Graph2D.h

@@ -8,7 +8,6 @@
 #include <set>
 #include <string>
 #include <utility>
-#include <vector>
 
 #include "DataType.h"
 #include "boost/multi_array.hpp"
@@ -35,7 +34,7 @@ class Graph2D
 
   struct NDRCongestion
   {
-    int net_id;  // NDR net id
+    int net_id;          // NDR net id
     uint16_t num_edges;  // number of congested edges
   };
 
@@ -119,6 +118,7 @@ class Graph2D
   void addCongestedNDRnet(int net_id, uint16_t num_edges);
   void sortCongestedNDRnets();
   int getOneCongestedNDRnet();
+  std::vector<int> getMultipleCongestedNDRnet();
 
  private:
   int x_grid_;

src/grt/src/fastroute/src/FastRoute.cpp

@@ -1194,7 +1194,7 @@ NetRouteMap FastRouteCore::run()
   float logistic_coef = 0;
   int slope;
   int max_adj;
-  const int long_edge_len = BIG_INT;
+  int long_edge_len = 40;
   const int short_edge_len = 12;
 
   // call FLUTE to generate RSMT and break the nets into segments (2-pin nets)
@@ -1348,9 +1348,6 @@ NetRouteMap FastRouteCore::run()
         if (i % 2 == 0) {
           logistic_coef += 0.5;
         }
-        // if (i > 40) {
-        //   break;
-        // }
       }
       if (i > 10) {
         ripup_threshold = 0;
@@ -1541,27 +1538,32 @@ NetRouteMap FastRouteCore::run()
       // Compute all the NDR nets involved in congestion
       computeCongestedNDRnets();
 
-      // Select one NDR net to be disabled
-      int net_id = graph2d_.getOneCongestedNDRnet();
+      std::vector<int> net_ids;
 
-      // If net_id == -1, there is no NDR net involved in congestion
-      if (net_id != -1) {
-        logger_->warn(
-            GRT, 273, "Disabling NDR net {}", nets_[net_id]->getName());
-
-        // Remove the usage of all the edges involved with this net
-        updateSoftNDRNetUsage(net_id, -nets_[net_id]->getEdgeCost());
-
-        // Reset the edge cost and layer edge cost to 1
-        setSoftNDR(net_id);
+      // If the congestion is not that high (note that the overflow is inflated
+      // by 100x when there is no capacity available for a NDR net in a specific
+      // edge)
+      if (total_overflow_ < 10000) {
+        // Select one NDR net to be disabled
+        int net_id = graph2d_.getOneCongestedNDRnet();
+        if (net_id != -1) {
+          net_ids.push_back(net_id);
+        }
+      } else {  // Select multiple NDR nets
+        net_ids = graph2d_.getMultipleCongestedNDRnet();
+      }
 
-        // Update the usage of all the edges involved with this net considering
-        // the new edge cost
-        updateSoftNDRNetUsage(net_id, nets_[net_id]->getEdgeCost());
+      // Only apply soft NDR if there is NDR nets involved in congestion
+      if (!net_ids.empty()) {
+        // Apply the soft NDR to the selected list of nets
+        applySoftNDR(net_ids);
 
         // Reset loop parameters
         overflow_increases = 0;
         i = 0;
+
+        // Increase maze route 3D threshold to fix bad routes
+        long_edge_len = BIG_INT;
       }
     }
 
@@ -1657,6 +1659,23 @@ NetRouteMap FastRouteCore::run()
   return routes;
 }
 
+void FastRouteCore::applySoftNDR(const std::vector<int>& net_ids)
+{
+  for (auto net_id : net_ids) {
+    logger_->warn(GRT, 273, "Disabling NDR net {}", nets_[net_id]->getName());
+
+    // Remove the usage of all the edges involved with this net
+    updateSoftNDRNetUsage(net_id, -nets_[net_id]->getEdgeCost());
+
+    // Reset the edge cost and layer edge cost to 1
+    setSoftNDR(net_id);
+
+    // Update the usage of all the edges involved with this net considering
+    // the new edge cost
+    updateSoftNDRNetUsage(net_id, nets_[net_id]->getEdgeCost());
+  }
+}
+
 void FastRouteCore::setSoftNDR(const int net_id)
 {
   nets_[net_id]->setIsSoftNDR(true);

src/grt/src/fastroute/src/graph2d.cpp

@@ -10,6 +10,7 @@
 #include <set>
 #include <string>
 #include <utility>
+#include <vector>
 
 #include "DataType.h"
 #include "FastRoute.h"
@@ -511,12 +512,24 @@ void Graph2D::sortCongestedNDRnets()
 
 int Graph2D::getOneCongestedNDRnet()
 {
-  if (!congested_ndrs_.empty() && congested_ndrs_[0].num_edges > 0) {
+  if (!congested_ndrs_.empty()) {
     return congested_ndrs_[0].net_id;
   }
   return -1;
 }
 
+// Get 10% of the NDR nets more involved in congestion
+std::vector<int> Graph2D::getMultipleCongestedNDRnet()
+{
+  std::vector<int> net_ids;
+  if (!congested_ndrs_.empty()) {
+    for (int i = 0; i < ceil((double)congested_ndrs_.size() / 10); i++) {
+      net_ids.push_back(congested_ndrs_[i].net_id);
+    }
+  }
+  return net_ids;
+}
+
 // Initializes the 3D capacity of the graph.
 void Graph2D::initCap3D()
 {