From efef777788aa9d0f112ba868aa41b8d6cc5cd99f Mon Sep 17 00:00:00 2001
From: Andres Rios Tascon <ariostas@gmail.com>
Date: Fri, 4 Oct 2024 06:21:52 -0700
Subject: [PATCH] Removed unnecessary CopyToHost

---
 RecoTracker/LSTCore/src/alpaka/Event.dev.cc | 19 ++++++++++++-------
 RecoTracker/LSTCore/src/alpaka/Event.h      |  2 +-
 RecoTracker/LSTCore/src/alpaka/Segment.h    | 13 -------------
 3 files changed, 13 insertions(+), 21 deletions(-)

diff --git a/RecoTracker/LSTCore/src/alpaka/Event.dev.cc b/RecoTracker/LSTCore/src/alpaka/Event.dev.cc
index 1bc0b6bc74976..521c4f2ee7046 100644
--- a/RecoTracker/LSTCore/src/alpaka/Event.dev.cc
+++ b/RecoTracker/LSTCore/src/alpaka/Event.dev.cc
@@ -1396,16 +1396,21 @@ MiniDoubletsBuffer<alpaka_common::DevHost>& Event::getMiniDoublets(bool sync) {
   return mdsInCPU_.value();
 }
 
-template <typename TSoA>
+template <typename TSoA, typename TDev>
 typename TSoA::ConstView Event::getSegments(bool sync) {
-  if constexpr (std::is_same_v<Device, DevHost>)
+  if constexpr (std::is_same_v<TDev, DevHost>) {
     return segmentsDev_->const_view<TSoA>();
-  if (!segmentsHost_) {
-    segmentsHost_.emplace(cms::alpakatools::CopyToHost<SegmentsDeviceCollection>::copyAsync(queue_, *segmentsDev_));
-    if (sync)
-      alpaka::wait(queue_);  // host consumers expect filled data
+  } else {
+    if (!segmentsHost_) {
+      segmentsHost_.emplace(
+          cms::alpakatools::
+              CopyToHost<PortableMultiCollection<TDev, SegmentsSoA, SegmentsOccupancySoA, SegmentsPixelSoA>>::copyAsync(
+                  queue_, *segmentsDev_));
+      if (sync)
+        alpaka::wait(queue_);  // host consumers expect filled data
+    }
+    return segmentsHost_->const_view<TSoA>();
   }
-  return segmentsHost_->const_view<TSoA>();
 }
 template SegmentsConst Event::getSegments<SegmentsSoA>(bool);
 template SegmentsOccupancyConst Event::getSegments<SegmentsOccupancySoA>(bool);
diff --git a/RecoTracker/LSTCore/src/alpaka/Event.h b/RecoTracker/LSTCore/src/alpaka/Event.h
index 398370438d0a5..c3a73c6d3ffad 100644
--- a/RecoTracker/LSTCore/src/alpaka/Event.h
+++ b/RecoTracker/LSTCore/src/alpaka/Event.h
@@ -183,7 +183,7 @@ namespace ALPAKA_ACCELERATOR_NAMESPACE::lst {
     HitsBuffer<DevHost>& getHitsInCMSSW(bool sync = true);
     ObjectRangesBuffer<DevHost>& getRanges(bool sync = true);
     MiniDoubletsBuffer<DevHost>& getMiniDoublets(bool sync = true);
-    template <typename TSoA>
+    template <typename TSoA, typename TDev = Device>
     typename TSoA::ConstView getSegments(bool sync = true);
     TripletsBuffer<DevHost>& getTriplets(bool sync = true);
     QuintupletsBuffer<DevHost>& getQuintuplets(bool sync = true);
diff --git a/RecoTracker/LSTCore/src/alpaka/Segment.h b/RecoTracker/LSTCore/src/alpaka/Segment.h
index 255be1741403e..79d5d93cc3bdc 100644
--- a/RecoTracker/LSTCore/src/alpaka/Segment.h
+++ b/RecoTracker/LSTCore/src/alpaka/Segment.h
@@ -910,17 +910,4 @@ namespace ALPAKA_ACCELERATOR_NAMESPACE::lst {
   };
 }  // namespace ALPAKA_ACCELERATOR_NAMESPACE::lst
 
-namespace cms::alpakatools {
-  // This is not used, but it is needed for compilation
-  template <typename T0, typename... Args>
-  struct CopyToHost<PortableHostMultiCollection<T0, Args...>> {
-    template <typename TQueue>
-    static auto copyAsync(TQueue& queue, PortableHostMultiCollection<T0, Args...> const& srcData) {
-      PortableHostMultiCollection<T0, Args...> dstData(srcData.sizes(), queue);
-      alpaka::memcpy(queue, dstData.buffer(), srcData.buffer());
-      return dstData;
-    }
-  };
-}  // namespace cms::alpakatools
-
 #endif