Address review comments

src/common/hist_util.cu

@@ -20,7 +20,6 @@
 
 #include "../data/adapter.h"
 #include "../data/device_adapter.cuh"
-#include "../tree/param.h"
 #include "device_helpers.cuh"
 #include "hist_util.h"
 #include "math.h"  // NOLINT
@@ -149,15 +148,15 @@ void ExtractCuts(int device, Span<SketchEntry> cuts,
 }
 
 /**
-* \brief Extracts the cuts from sorted data, considering weights.
-*
-* \param device                The device.
-* \param cuts                  Output cuts
-* \param num_cuts_per_feature  Number of cuts per feature.
-* \param sorted_data           Sorted entries in segments of columns
-* \param column_sizes_scan     Describes the boundaries of column segments in
-* sorted data
-*/
+ * \brief Extracts the cuts from sorted data, considering weights.
+ *
+ * \param device                The device.
+ * \param cuts                  Output cuts.
+ * \param num_cuts_per_feature  Number of cuts per feature.
+ * \param sorted_data           Sorted entries in segments of columns.
+ * \param weights_scan          Inclusive scan of weights for each entry in sorted_data.
+ * \param column_sizes_scan     Describes the boundaries of column segments in sorted data.
+ */
 void ExtractWeightedCuts(int device, Span<SketchEntry> cuts,
                          size_t num_cuts_per_feature, Span<Entry> sorted_data,
                          Span<float> weights_scan,
@@ -259,7 +258,6 @@ void ProcessWeightedBatch(int device, const SparsePage& page,
   thrust::sort_by_key(thrust::cuda::par(alloc), sorted_entries.begin(),
                       sorted_entries.end(), temp_weights.begin(),
                       EntryCompareOp());
-  std::vector<Entry> entries_t(sorted_entries.begin(), sorted_entries.end());
 
   // Scan weights
   thrust::inclusive_scan_by_key(thrust::cuda::par(alloc),
@@ -268,7 +266,6 @@ void ProcessWeightedBatch(int device, const SparsePage& page,
                                 [=] __device__(const Entry& a, const Entry& b) {
                                   return a.index == b.index;
                                 });
-  std::vector<float> weights_t(temp_weights.begin(), temp_weights.end());
 
   dh::caching_device_vector<size_t> column_sizes_scan;
   GetColumnSizesScan(device, &column_sizes_scan,
@@ -308,7 +305,7 @@ HistogramCuts DeviceSketch(int device, DMatrix* dmat, int max_bins,
   }
   dmat->Info().weights_.SetDevice(device);
   for (const auto& batch : dmat->GetBatches<SparsePage>()) {
-    size_t batch_nnz = batch.data.ConstHostVector().size();
+    size_t batch_nnz = batch.data.Size();
     for (auto begin = 0ull; begin < batch_nnz;
          begin += sketch_batch_num_elements) {
       size_t end = std::min(batch_nnz, size_t(begin + sketch_batch_num_elements));
@@ -345,9 +342,10 @@ struct IsValidFunctor : public thrust::unary_function<Entry, bool> {
   }
 };
 
+// Thrust version of this function causes error on Windows
 template <typename ReturnT, typename IterT, typename FuncT>
 thrust::transform_iterator<FuncT, IterT, ReturnT> MakeTransformIterator(
-    IterT iter, FuncT func) {
+  IterT iter, FuncT func) {
   return thrust::transform_iterator<FuncT, IterT, ReturnT>(iter, func);
 }
 
@@ -357,19 +355,17 @@ void ProcessBatch(AdapterT* adapter, size_t begin, size_t end, float missing,
   dh::XGBCachingDeviceAllocator<char> alloc;
   adapter->BeforeFirst();
   adapter->Next();
-  auto& batch = adapter->Value();
+  auto &batch = adapter->Value();
   // Enforce single batch
   CHECK(!adapter->Next());
-
   auto batch_iter = MakeTransformIterator<data::COOTuple>(
-      thrust::make_counting_iterator(0llu),
-      [=] __device__(size_t idx) { return batch.GetElement(idx); });
+    thrust::make_counting_iterator(0llu),
+    [=] __device__(size_t idx) { return batch.GetElement(idx); });
   auto entry_iter = MakeTransformIterator<Entry>(
       thrust::make_counting_iterator(0llu), [=] __device__(size_t idx) {
         return Entry(batch.GetElement(idx).column_idx,
                      batch.GetElement(idx).value);
       });
-
   // Work out how many valid entries we have in each column
   dh::caching_device_vector<size_t> column_sizes_scan(adapter->NumColumns() + 1,
                                                       0);