TrackingRecHitsSoACollection: early return hostData when there aren't hits

Author: mmusich

DataFormats/TrackingRecHitSoA/interface/alpaka/TrackingRecHitsSoACollection.h

@@ -34,6 +34,16 @@ namespace cms::alpakatools {
     template <typename TQueue>
     static auto copyAsync(TQueue& queue, TrackingRecHitDevice<TrackerTraits, TDevice> const& deviceData) {
       TrackingRecHitHost<TrackerTraits> hostData(queue, deviceData.view().metadata().size());
+
+      // Don't bother if zero hits
+      if (deviceData.view().metadata().size() == 0) {
+        std::memset(hostData.buffer().data(),
+                    0,
+                    alpaka::getExtentProduct(hostData.buffer()) *
+                        sizeof(alpaka::Elem<typename TrackingRecHitHost<TrackerTraits>::Buffer>));
+        return hostData;
+      }
+
       alpaka::memcpy(queue, hostData.buffer(), deviceData.buffer());
 #ifdef GPU_DEBUG
       printf("TrackingRecHitsSoACollection: I'm copying to host.\n");

RecoTracker/PixelSeeding/plugins/alpaka/CAHitNtupletGenerator.cc

@@ -299,6 +299,10 @@ namespace ALPAKA_ACCELERATOR_NAMESPACE {
 
     TrackSoA tracks(queue);
 
+    // Don't bother if less than 2 this
+    if (hits_d.view().metadata().size() < 2)
+      return tracks;
+
     GPUKernels kernels(m_params, hits_d.view().metadata().size(), hits_d.offsetBPIX2(), queue);
 
     kernels.buildDoublets(hits_d.view(), hits_d.offsetBPIX2(), queue);