fix

src/common/hist_util.h

@@ -181,6 +181,29 @@ using BinTypeSizeSequence = std::integer_sequence<uint32_t,
   BinTypeSize::kUint32BinsTypeSize>;
 using BoolSequence = std::integer_sequence<bool, true, false>;
 
+
+
+/**
+ * \brief Dispatch for bin type, fn is a function that accepts a scalar of the bin type.
+ */
+template <typename Fn>
+auto DispatchBinType(BinTypeSize type, Fn&& fn) {
+  switch (type) {
+    case kUint8BinsTypeSize: {
+      return fn(uint8_t{});
+    }
+    case kUint16BinsTypeSize: {
+      return fn(uint16_t{});
+    }
+    case kUint32BinsTypeSize: {
+      return fn(uint32_t{});
+    }
+  }
+  LOG(FATAL) << "Unreachable";
+  return fn(uint32_t{});
+}
+
+
 /**
  * \brief Optionally compressed gradient index. The compression works only with dense
  *        data.

src/data/gradient_index.h

@@ -82,7 +82,6 @@ class GHistIndexMatrix {
   GHistIndexMatrix(DMatrix* x, bst_bin_t max_bins_per_feat, double sparse_thresh,
                    bool sorted_sketch, int32_t n_threads, common::Span<float> hess = {});
   ~GHistIndexMatrix();
-
   // Create a global histogram matrix, given cut. Used by external memory
   void Init(SparsePage const& page, common::Span<FeatureType const> ft,
             common::HistogramCuts const& cuts, int32_t max_bins_per_feat, bool is_dense,