blazingly fasterer

src/PIM/Dialect/Spatial/Transforms/MergeComputeNodes/Scheduling/PeftScheduler.cpp

@@ -133,6 +133,22 @@ void verifyOctTableSize(size_t nodeCount, size_t processorCount) {
   }
 }
 
+bool hasHighCrossbarPressure(const ComputeGraph& graph, size_t processorCount, size_t crossbarCapacity) {
+  if (crossbarCapacity > std::numeric_limits<size_t>::max() / processorCount)
+    return false;
+  const size_t threshold = processorCount * crossbarCapacity / 2;
+  CrossbarUsage distinctWeights;
+  for (const ComputeGraphNode& node : graph.nodes) {
+    for (const CrossbarWeight& weight : node.crossbarUsage) {
+      if (!containsCrossbarWeight(distinctWeights, weight))
+        distinctWeights.push_back(weight);
+      if (distinctWeights.size() > threshold)
+        return true;
+    }
+  }
+  return false;
+}
+
 } // namespace
 
 Time getPeftTransferTime(Time transferCost, size_t sourceProcessor, size_t targetProcessor, size_t processorCount) {
@@ -145,6 +161,7 @@ MergeScheduleResult runPeftScheduler(const ComputeGraph& graph, const PeftSchedu
   if (processorCount == 0)
     llvm::report_fatal_error("PEFT scheduler: processor count must be positive");
   MeshModel mesh = MeshModel::infer(processorCount);
+  const bool preferCrossbarReuse = hasHighCrossbarPressure(graph, processorCount, options.crossbarCapacity);
 
   verifyOctTableSize(nodeCount, processorCount);
   std::vector<std::vector<size_t>> reverseLevels = buildReverseLevels(graph);
@@ -282,6 +299,8 @@ MergeScheduleResult runPeftScheduler(const ComputeGraph& graph, const PeftSchedu
       Time eft = addOrMax(est, computeCost);
       Time oeft = addOrMax(eft, oct[task * processorCount + processor]);
       size_t centerDistance = mesh.getCenterDistance(processor);
+      bool betterCrossbarChoice =
+        preferCrossbarReuse ? overlapCount > bestOverlapCount : overlapCount < bestOverlapCount;
 
       if (oeft < bestOeft || (oeft == bestOeft && eft < bestEft)
           || (oeft == bestOeft && eft == bestEft && est < bestEst)) {
@@ -302,7 +321,7 @@ MergeScheduleResult runPeftScheduler(const ComputeGraph& graph, const PeftSchedu
         bestCenterDistance = centerDistance;
       }
       else if (oeft == bestOeft && eft == bestEft && est == bestEst
-               && centerDistance == bestCenterDistance && overlapCount < bestOverlapCount) {
+               && centerDistance == bestCenterDistance && betterCrossbarChoice) {
         bestProcessor = processor;
         bestEst = est;
         bestEft = eft;