Copy data from Ellpack to GHist. (#8215)

src/common/device_helpers.cuh

@@ -35,6 +35,7 @@
 #include "xgboost/global_config.h"
 
 #include "common.h"
+#include "algorithm.cuh"
 
 #ifdef XGBOOST_USE_NCCL
 #include "nccl.h"
@@ -1556,17 +1557,7 @@ XGBOOST_DEVICE thrust::transform_iterator<FuncT, IterT, ReturnT> MakeTransformIt
   return thrust::transform_iterator<FuncT, IterT, ReturnT>(iter, func);
 }
 
-template <typename It>
-size_t XGBOOST_DEVICE SegmentId(It first, It last, size_t idx) {
-  size_t segment_id = thrust::upper_bound(thrust::seq, first, last, idx) -
-                      1 - first;
-  return segment_id;
-}
-
-template <typename T>
-size_t XGBOOST_DEVICE SegmentId(xgboost::common::Span<T> segments_ptr, size_t idx) {
-  return SegmentId(segments_ptr.cbegin(), segments_ptr.cend(), idx);
-}
+using xgboost::common::cuda::SegmentId;  // import it for compatibility
 
 namespace detail {
 template <typename Key, typename KeyOutIt>